
In the
philosophy of mind
Philosophy of mind is a branch of philosophy that deals with the nature of the mind and its relation to the Body (biology), body and the Reality, external world.
The mind–body problem is a paradigmatic issue in philosophy of mind, although a ...
, mind–body dualism denotes either that
mental phenomena are
non-physical,
[ Hart, W. D. 1996. "Dualism." pp. 265–267 in ''A Companion to the Philosophy of Mind'', edited by S. Guttenplan. Oxford: Blackwell.] or that the
mind
The mind is that which thinks, feels, perceives, imagines, remembers, and wills. It covers the totality of mental phenomena, including both conscious processes, through which an individual is aware of external and internal circumstances ...
and
body are distinct and separable.
Thus, it encompasses a set of views about the relationship between mind and matter, as well as between
subject and
object, and is contrasted with other positions, such as
physicalism and
enactivism, in the
mind–body problem
The mind–body problem is a List_of_philosophical_problems#Mind–body_problem, philosophical problem concerning the relationship between thought and consciousness in the human mind and Human body, body. It addresses the nature of consciousness ...
.
Aristotle
Aristotle (; 384–322 BC) was an Ancient Greek philosophy, Ancient Greek philosopher and polymath. His writings cover a broad range of subjects spanning the natural sciences, philosophy, linguistics, economics, politics, psychology, a ...
shared
Plato
Plato ( ; Greek language, Greek: , ; born BC, died 348/347 BC) was an ancient Greek philosopher of the Classical Greece, Classical period who is considered a foundational thinker in Western philosophy and an innovator of the writte ...
's view of multiple
souls and further elaborated a hierarchical arrangement, corresponding to the distinctive functions of plants, animals, and humans: a nutritive soul of growth and
metabolism
Metabolism (, from ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the co ...
that all three share; a perceptive soul of pain, pleasure, and desire that only humans and other animals share; and the faculty of reason that is unique to humans only. In this view, a soul is the
hylomorphic form of a viable organism, wherein each level of the hierarchy formally
supervenes upon the
substance of the preceding level. For Aristotle, the first two souls, based on the body, perish when the living organism dies,
[Aristotle. . mid 4th century BC1924. '' Metaphysics (Metaphysica)'', edited by W. D. Ross. Oxford: Oxford University Press, 2 vols.] whereas there remains an immortal and perpetual intellective part of mind. For Plato, however, the soul was not dependent on the physical body; he believed in
metempsychosis, the migration of the soul to a new physical body.
[Duke, E. A., W. F. Hicken, W. S. M. Nicoll, et al., eds. 1995. ''Platonis Opera, Vol. 1: Tetralogiae I-II'', Oxford Classical Texts. Oxford: Clarendon Press. . (includes '']Euthyphro
''Euthyphro'' (; ), is a philosophical work by Plato written in the form of a Socratic dialogue set during the weeks before the trial of Socrates in 399 BC. In the dialogue, Socrates and Euthyphro attempt to establish a definition of '' piet ...
'', '' Apologia Socratis'', '' Crito'', '' Phaedo'', '' Cratylus'', '' Theaetetus'', '' Sophistes'', and '' Politicus''.) It has been considered a form of reductionism by some philosophers, since it enables the tendency to ignore very big groups of variables by its assumed association with the mind or the body, and not for its real value when it comes to explaining or predicting a studied phenomenon.
Dualism is closely associated with the thought of
René Descartes
René Descartes ( , ; ; 31 March 1596 – 11 February 1650) was a French philosopher, scientist, and mathematician, widely considered a seminal figure in the emergence of modern philosophy and Modern science, science. Mathematics was paramou ...
(1641), who holds that the mind is a nonphysical—and therefore, non-spatial—substance. Descartes clearly identified the mind with
consciousness
Consciousness, at its simplest, is awareness of a state or object, either internal to oneself or in one's external environment. However, its nature has led to millennia of analyses, explanations, and debate among philosophers, scientists, an ...
and self-awareness and distinguished this from the physical brain as the seat of
intelligence
Intelligence has been defined in many ways: the capacity for abstraction, logic, understanding, self-awareness, learning, emotional knowledge, reasoning, planning, creativity, critical thinking, and problem-solving. It can be described as t ...
.
[ Robinson, Howard. 0032016.]
Dualism
(rev.). ''The Stanford Encyclopedia of Philosophy
The ''Stanford Encyclopedia of Philosophy'' (''SEP'') is a freely available online philosophy resource published and maintained by Stanford University, encompassing both an online encyclopedia of philosophy and peer-reviewed original publication ...
'', edited by Edward N. Zalta. Hence, he was the first documented Western philosopher to formulate the mind–body problem in the form in which it exists today.
[ Descartes, René. 6411984. " Meditations on First Philosophy." pp. 1–62 in ''The Philosophical Writings of René Descartes'' 2, translated by J. Cottingham, R. Stoothoff, and D. Murdoch. Cambridge: Cambridge University Press.] However, the theory of substance dualism has many advocates in contemporary philosophy such as
Richard Swinburne, William Hasker,
J. P. Moreland, E. J. Low,
Charles Taliaferro, Seyyed Jaaber Mousavirad, and John Foster.
Dualism is contrasted with various kinds of
monism.
Substance dualism is contrasted with all forms of
materialism
Materialism is a form of monism, philosophical monism according to which matter is the fundamental Substance theory, substance in nature, and all things, including mind, mental states and consciousness, are results of material interactions. Acco ...
, but
property dualism may be considered a form of
non-reductive physicalism.
Types
Ontological dualism makes dual commitments about the nature of existence as it relates to mind and matter, and can be divided into three different types:
# ''
Substance dualism'' asserts that mind and matter are fundamentally distinct kinds of foundations.
# ''
Property dualism'' suggests that the ontological distinction lies in the differences between properties of mind and matter (as in
emergentism).
# ''
Predicate dualism'' claims the irreducibility of mental predicates to physical predicates.
Substance or Cartesian dualism
Substance dualism asserts that mind and matter are fundamentally distinct kinds of foundations. There are different types of substance dualism. Most substance dualists hold the view that the mind and body are capable of causally affecting each other, known as
interactionism. Notable defenders of substance dualism include
John Foster,
Stewart Goetz,
Richard Swinburne and
Charles Taliaferro.
Cartesian dualism, most famously defended by
René Descartes
René Descartes ( , ; ; 31 March 1596 – 11 February 1650) was a French philosopher, scientist, and mathematician, widely considered a seminal figure in the emergence of modern philosophy and Modern science, science. Mathematics was paramou ...
, argues that there are two kinds of substances: mental and physical.
Descartes states that the mental can exist outside of the body, and the body cannot think. Substance dualism is important historically for having given rise to much thought regarding the famous
mind–body problem
The mind–body problem is a List_of_philosophical_problems#Mind–body_problem, philosophical problem concerning the relationship between thought and consciousness in the human mind and Human body, body. It addresses the nature of consciousness ...
. It is compatible with theologies which claim that immortal souls occupy an independent realm of existence distinct from that of the physical world.
Cartesians tend to equate the soul to the mind.
The
Copernican Revolution and the scientific discoveries of the 17th century reinforced the belief that the scientific method was the unique way of knowledge. Bodies were seen as biological organisms to be studied in their constituent parts (materialism) by means of
anatomy
Anatomy () is the branch of morphology concerned with the study of the internal structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old scien ...
,
physiology
Physiology (; ) is the science, scientific study of function (biology), functions and mechanism (biology), mechanisms in a life, living system. As a branches of science, subdiscipline of biology, physiology focuses on how organisms, organ syst ...
,
biochemistry
Biochemistry, or biological chemistry, is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology, a ...
and physics (reductionism).
Mind–body dualism remained the biomedical paradigm and model for the following three centuries.
Emergent dualism
Emergent dualism is a type of substance dualism that has been defended by
William Hasker and
Dean Zimmerman.
Emergent dualism asserts that mental substances come into existence when physical systems such as the brain reach a sufficient level of complexity.
Hasker defines emergent dualism as:
Hasker has argued that emergent dualism is consistent with neuroscientific discoveries showing the dependence of mind on brain.
He likens the individual mind to a magnetic field in its qualitative difference from the physical properties that generate it and also in its ability to act on the brain that generates it.
Consciousness is said to arise when the brain reaches a certain threshold level of organizational complexity and when properly organized gives rise to the soul.
Thomistic dualism
Thomistic dualism is a type of dualism derived from the views of
Thomas Aquinas
Thomas Aquinas ( ; ; – 7 March 1274) was an Italian Dominican Order, Dominican friar and Catholic priest, priest, the foremost Scholasticism, Scholastic thinker, as well as one of the most influential philosophers and theologians in the W ...
.
Edward Feser has written that:
Thomistic substance dualism has been defended by
J. P. Moreland and
Scott B. Rae.
Thomistic substance dualism distinguishes itself from Cartesian substance dualism by denying that the body and soul are different substances. Instead, a person is composed of only one substance the soul while the body is considered an ensouled physical structure.
J. P. Moreland has commented:
Eleonore Stump has suggested that
Thomas Aquinas
Thomas Aquinas ( ; ; – 7 March 1274) was an Italian Dominican Order, Dominican friar and Catholic priest, priest, the foremost Scholasticism, Scholastic thinker, as well as one of the most influential philosophers and theologians in the W ...
's views on matter and the soul are difficult to define in contemporary discussion but he would fit the criteria as a non-Cartesian substance dualist.
Other terms for Thomistic dualism include hylomorphic dualism or
Thomistic hylomorphism which are contrasted with substance dualism.
Hylomorphism is distinct from substance dualism as it holds the view that the immaterial (form) and material (matter) are not distinct substances and only share an efficient causality.
Thomistic scholars such as Paul Chutikorn and Edward Feser have written that Aquinas was not a substance dualist.
Edward Feser who has defended hylomorphic dualism has suggested that it has advantages over substance dualism such as offering a possible solution to the interaction problem.
Paul Chutikorn has commented that "adopting Aquinas' view of substance will provide a solution to the problem by avoiding altogether the position that man is made up of dual substances. Rather, Aquinas shows us that we can acknowledge a duality within substance itself, while maintaining its inherent substantial unity".
Aristotelian hylomorphic dualism also has many similarities with Thomistic dualism.
Michael Egnor is a notable advocate of Aristotelian dualism.
Property dualism
Property dualism asserts that an ontological distinction lies in the differences between properties of mind and matter, and that consciousness may be ontologically irreducible to
neurobiology and physics. It asserts that when matter is organized in the appropriate way (i.e., in the way that living human bodies are organized), mental properties emerge. Hence, it is a sub-branch of
emergent materialism. What views properly fall under the ''property dualism'' rubric is itself a matter of dispute. There are different versions of property dualism, some of which claim independent categorisation.
[ Searle, John. 9832002.]
Why I Am Not a Property Dualist
" Archived from th
original
on 10 December 2006.
Non-reductive physicalism is a form of property dualism in which it is asserted that all mental states are causally reducible to physical states. One argument for this has been made in the form of
anomalous monism expressed by
Donald Davidson, where it is argued that mental events are identical to physical events, however, strict law-governed causal relationships cannot describe relations of mental events. Another argument for this has been expressed by
John Searle
John Rogers Searle (; born July 31, 1932) is an American philosopher widely noted for contributions to the philosophy of language, philosophy of mind, and social philosophy. He began teaching at UC Berkeley in 1959 and was Willis S. and Mario ...
, who is the advocate of a distinctive form of physicalism he calls
biological naturalism. His view is that although mental states are ontologically irreducible to physical states, they are
causally reducible. He has acknowledged that "to many people" his views and those of property dualists look a lot alike, but he thinks the comparison is misleading.
Epiphenomenalism
Epiphenomenalism is a form of property dualism, in which it is asserted that one or more mental states do not have any influence on physical states (both ontologically and causally irreducible). It asserts that while material causes give rise to
sensations,
volitions,
idea
In philosophy and in common usage, an idea (from the Greek word: ἰδέα (idea), meaning 'a form, or a pattern') is the results of thought. Also in philosophy, ideas can also be mental representational images of some object. Many philosophe ...
s, etc., such mental phenomena themselves cause nothing further: they are causal dead-ends. This can be contrasted to
interactionism, on the other hand, in which mental causes can produce material effects, and vice versa.
[ Robinson, Howard. 2003. "Dualism." pp. 85–101 in ''The Blackwell Guide to Philosophy of Mind'', edited by S. Stich and T. Warfield. Oxford: Blackwell.]
Predicate dualism
Predicate dualism is a view espoused by such non-reductive physicalists as
Donald Davidson and
Jerry Fodor, who maintain that while there is only one ontological category of substances and properties of substances (usually physical), the predicates that we use to describe mental events cannot be redescribed in terms of (or reduced to) physical predicates of natural languages.
[Davidson, Donald. 1980. ''Essays on Actions and Events''. Oxford University Press. .]
''Predicate dualism'' is most easily defined as the negation of ''predicate monism''. Predicate monism can be characterized as the view subscribed to by
eliminative materialists, who maintain that such intentional predicates as ''believe'', ''desire'', ''think'', ''feel'', etc., will eventually be eliminated from both the language of science and from ordinary language because the entities to which they refer do not exist. Predicate dualists believe that so-called "
folk psychology
Folk psychology, commonsense psychology, or naïve psychology is the ordinary, intuitive, or non-expert understanding, explanation, and rationalization of people's behaviors and Cognitive psychology, mental states. In philosophy of mind and cognit ...
," with all of its
propositional attitude
A propositional attitude is a mental state held by an agent or organism toward a proposition. In philosophy, propositional attitudes can be considered to be neurally realized, causally efficacious, content-bearing internal states (personal princip ...
ascriptions, is an ineliminable part of the enterprise of describing, explaining, and understanding human mental states and behavior.
For example, Davidson subscribes to
anomalous monism, according to which there can be no strict psychophysical laws which connect mental and physical events under their descriptions as ''mental'' and ''physical'' events. However, all mental events also have physical descriptions. It is in terms of the latter that such events can be connected in law-like relations with other physical events. Mental predicates are irreducibly different in character (rational, holistic, and necessary) from physical predicates (contingent, atomic, and causal).
Dualist views of mental causation

This part is about causation between properties and states of the thing under study, not its substances or predicates. Here a state is the set of all properties of what's being studied. Thus each state describes only one point in time.
Interactionism
Interactionism is the view that mental states, such as beliefs and desires, causally interact with physical states. This is a position which is very appealing to common-sense intuitions, notwithstanding the fact that it is very difficult to establish its validity or correctness by way of
logic
Logic is the study of correct reasoning. It includes both formal and informal logic. Formal logic is the study of deductively valid inferences or logical truths. It examines how conclusions follow from premises based on the structure o ...
al argumentation or empirical proof. It seems to appeal to common-sense because we are surrounded by such everyday occurrences as a child's touching a hot stove (physical event) which causes him to feel pain (mental event) and then yell and scream (physical event) which causes his parents to experience a sensation of fear and protectiveness (mental event) and so on.
Epiphenomenalism
Epiphenomenalism states that all mental events are caused by a physical event and have no physical consequences, and that one or more mental states do not have any influence on physical states. So, the mental event of deciding to pick up a rock ("''M1''") is caused by the firing of specific neurons in the brain ("''P1''"). When the arm and hand move to pick up the rock ("''P2''") this is not caused by the preceding mental event ''M1'', nor by ''M1'' and ''P1'' together, but only by ''P1''. The physical causes are in principle reducible to fundamental physics, and therefore mental causes are eliminated using this
reductionist explanation. If P1 causes both ''M1'' and ''P2'', there is no
overdetermination in the explanation for ''P2''.
The idea that even if the animal were conscious nothing would be added to the production of behavior, even in animals of the human type, was first voiced by
La Mettrie (1745), and then by
Cabanis (1802), and was further explicated by
Hodgson (1870) and
Huxley (1874).
Jackson gave a
subjective argument for epiphenomenalism, but later rejected it and embraced
physicalism.
Parallelism
Psychophysical parallelism is a very unusual view about the interaction between mental and physical events which was most prominently, and perhaps ''only'' truly, advocated by
Gottfried Wilhelm von Leibniz. Like Malebranche and others before him, Leibniz recognized the weaknesses of Descartes' account of causal interaction taking place in a physical location in the brain. Malebranche decided that such a material basis of interaction between material and immaterial was impossible and therefore formulated his doctrine of
occasionalism, stating that the interactions were really caused by the intervention of God on each individual occasion. Leibniz's idea is that God has created a
pre-established harmony such that it only seems ''as if'' physical and mental events cause, and are caused by, one another. In reality, mental causes only have mental effects and physical causes only have physical effects. Hence, the term ''parallelism'' is used to describe this view.
Occasionalism
Occasionalism is a philosophical doctrine about causation which says that created substances cannot be efficient causes of events. Instead, all events are taken to be caused directly by God itself. The theory states that the illusion of efficient causation between mundane events arises out of a constant conjunction that God had instituted, such that every instance where the cause is present will constitute an "occasion" for the effect to occur as an expression of the aforementioned power. This "occasioning" relation, however, falls short of efficient causation. In this view, it is not the case that the first event causes God to cause the second event: rather, God first caused one and then caused the other, but chose to regulate such behaviour in accordance with general laws of nature. Some of its most prominent historical exponents have been
Al-Ghazali,
Louis de la Forge,
Arnold Geulincx, and
Nicolas Malebranche.
Kantianism
According to the philosophy of
Immanuel Kant
Immanuel Kant (born Emanuel Kant; 22 April 1724 – 12 February 1804) was a German Philosophy, philosopher and one of the central Age of Enlightenment, Enlightenment thinkers. Born in Königsberg, Kant's comprehensive and systematic works ...
, there is a distinction between actions done by desire and those performed by reason in liberty (
categorical imperative
The categorical imperative () is the central philosophical concept in the deontological Kantian ethics, moral philosophy of Immanuel Kant. Introduced in Kant's 1785 ''Groundwork of the Metaphysics of Morals'', it is a way of evaluating motivati ...
). Thus, not all physical actions are caused either by matter alone or by freedom alone. Some actions are purely animal in nature, while others are the result of mind's free action on matter.
History
Ancient Greek philosophy
Hermotimus of Clazomenae (fl. c. 6th century BCE) was a philosopher who first proposed the idea of mind being fundamental in the cause of change. He proposed that physical entities are static, while reason causes the change.
Sextus Empiricus places him with
Hesiod,
Parmenides
Parmenides of Elea (; ; fl. late sixth or early fifth century BC) was a Pre-Socratic philosophy, pre-Socratic ancient Greece, Greek philosopher from Velia, Elea in Magna Graecia (Southern Italy).
Parmenides was born in the Greek colony of Veli ...
, and
Empedocles, as belonging to the class of philosophers who held a dualistic theory of a material and an active principle being together the origin of the universe. Similar ideas were expounded by
Anaxagoras
Anaxagoras (; , ''Anaxagóras'', 'lord of the assembly'; ) was a Pre-Socratic Greek philosopher. Born in Clazomenae at a time when Asia Minor was under the control of the Persian Empire, Anaxagoras came to Athens. In later life he was charged ...
.
In the dialogue ''
Phaedo'',
Plato
Plato ( ; Greek language, Greek: , ; born BC, died 348/347 BC) was an ancient Greek philosopher of the Classical Greece, Classical period who is considered a foundational thinker in Western philosophy and an innovator of the writte ...
formulated his famous
Theory of forms as distinct and immaterial substances of which the objects and other phenomena that we perceive in the world are nothing more than mere shadows.
In the ''Phaedo'', Plato makes it clear that the Forms are the ''universalia ante res'', i.e. they are ideal universals, by which we are able to understand the world. In his
allegory of the cave, Plato likens the achievement of philosophical understanding to emerging into
the sunlight from a dark cave, where only vague shadows of what lies beyond that prison are cast dimly upon the wall. Plato's forms are non-physical and non-mental. They exist nowhere in time or space, but neither do they exist in the mind, nor in the
pleroma
Pleroma (, literally "fullness") generally refers to the totality of divine powers. It is used in Christian theological contexts, as well as in Gnosticism. The term also appears in the Epistle to the Colossians, which is traditionally attributed ...
of matter; rather, matter is said to "participate" in form (μεθεξις, ''
methexis''). It remained unclear however, even to Aristotle, exactly what Plato intended by that.
Aristotle
Aristotle (; 384–322 BC) was an Ancient Greek philosophy, Ancient Greek philosopher and polymath. His writings cover a broad range of subjects spanning the natural sciences, philosophy, linguistics, economics, politics, psychology, a ...
argued at length against many aspects of Plato's forms, creating his own doctrine of
hylomorphism wherein form and matter coexist. Ultimately however, Aristotle's aim was to perfect a theory of forms, rather than to reject it. Although Aristotle strongly rejected the independent existence Plato attributed to forms, his
metaphysics
Metaphysics is the branch of philosophy that examines the basic structure of reality. It is traditionally seen as the study of mind-independent features of the world, but some theorists view it as an inquiry into the conceptual framework of ...
do agree with Plato's ''
a priori
('from the earlier') and ('from the later') are Latin phrases used in philosophy to distinguish types of knowledge, Justification (epistemology), justification, or argument by their reliance on experience. knowledge is independent from any ...
'' considerations quite often. For example, Aristotle argues that changeless, eternal substantial form is necessarily immaterial. Because matter provides a stable substratum for a change in form, matter always has the potential to change. Thus, if given an eternity in which to do so, it ''will'', necessarily, exercise that potential.
Part of Aristotle's ''psychology'', the study of the soul, is his account of the ability of humans to reason and the ability of animals to perceive. In both cases, perfect copies of forms are acquired, either by direct impression of environmental forms, in the case of perception, or else by virtue of contemplation, understanding and recollection. He believed the mind can literally assume any form being contemplated or experienced, and it was unique in its ability to become a blank slate, having no essential form. As thoughts of earth are not heavy, any more than thoughts of fire are causally efficient, they provide an immaterial complement for the formless mind.
[Aristotle. . mid 4th century BC1907. '' On the Soul (De anima)'', edited by R. D. Hicks. Cambridge: Cambridge University Press; 1968. Books II-III, translated by D.W. Hamlyn, Clarendon Aristotle Series. Oxford: Oxford University Press.]
From Neoplatonism to scholasticism
The philosophical school of
Neoplatonism, most active in Late Antiquity, claimed that the physical and the spiritual are both emanations of ''the One''. Neoplatonism exerted a considerable influence on Christianity, as did the philosophy of Aristotle via
scholasticism
Scholasticism was a medieval European philosophical movement or methodology that was the predominant education in Europe from about 1100 to 1700. It is known for employing logically precise analyses and reconciling classical philosophy and Ca ...
.
In the scholastic tradition of
Saint Thomas Aquinas, a number of whose doctrines have been incorporated into Roman Catholic
dogma, the soul is the substantial form of a human being.
Aquinas held the ''Quaestiones disputate de anima'', or 'Disputed questions on the soul', at the Roman ''studium provinciale'' of the
Dominican Order
The Order of Preachers (, abbreviated OP), commonly known as the Dominican Order, is a Catholic Church, Catholic mendicant order of pontifical right that was founded in France by a Castilians, Castilian priest named Saint Dominic, Dominic de Gu ...
at
Santa Sabina, the forerunner of the
Pontifical University of Saint Thomas Aquinas, ''Angelicum'' during the academic year 1265–1266. By 1268 Aquinas had written at least the first book of the ''Sententia Libri De anima'', Aquinas' commentary on Aristotle's ''
De anima'', the translation of which from the Greek was completed by Aquinas' Dominican associate at
Viterbo,
William of Moerbeke in 1267. Like Aristotle, Aquinas held that the human being was a unified composite substance of two substantial principles: form and matter. The soul is the substantial form and so the first actuality of a material organic body with the potentiality for life.
While Aquinas defended the unity of human nature as a composite substance constituted by these two inextricable principles of form and matter, he also argued for the incorruptibility of the intellectual soul,
in contrast to the corruptibility of the vegetative and sensitive animation of plants and animals.
His argument for the subsistence and incorruptibility of the intellectual soul takes its point of departure from the metaphysical principle that operation follows upon being (''agiture sequitur esse''), i.e., the activity of a thing reveals the mode of being and existence it depends upon. Since the intellectual soul exercises its own ''per se'' intellectual operations without employing material faculties, i.e. intellectual operations are immaterial, the intellect itself and the intellectual soul, must likewise be immaterial and so incorruptible. Even though the intellectual soul of man is able to subsist upon the death of the human being, Aquinas does not hold that the human person is able to remain integrated at death. The separated intellectual soul is neither a man nor a human person. The intellectual soul ''by itself'' is ''not'' a human person (i.e., an individual ''supposit'' of a rational nature). Hence, Aquinas held that "soul of St. Peter pray for us" would be more appropriate than "St. Peter pray for us", because all things connected with his person, including memories, ended with his corporeal life.
The
Catholic
The Catholic Church (), also known as the Roman Catholic Church, is the List of Christian denominations by number of members, largest Christian church, with 1.27 to 1.41 billion baptized Catholics Catholic Church by country, worldwid ...
doctrine of the
resurrection of the body does not subscribe that, sees body and soul as forming a whole and states that at the
second coming
The Second Coming (sometimes called the Second Advent or the Parousia) is the Christianity, Christian and Islam, Islamic belief that Jesus, Jesus Christ will return to Earth after his Ascension of Jesus, ascension to Heaven (Christianity), Heav ...
, the souls of the departed will be reunited with their bodies as a whole person (substance) and witness to the
apocalypse. The thorough consistency between dogma and contemporary science was maintained here in part from a serious attendance to the principle that there can be only one truth. Consistency with science, logic, philosophy, and faith remained a high priority for centuries, and a university doctorate in theology generally included the entire science curriculum as a prerequisite. This doctrine is not universally accepted by Christians today. Many believe that one's immortal soul goes directly to
Heaven
Heaven, or the Heavens, is a common Religious cosmology, religious cosmological or supernatural place where beings such as deity, deities, angels, souls, saints, or Veneration of the dead, venerated ancestors are said to originate, be throne, ...
upon death of the body.
Descartes and his disciples
In his ''
Meditations on First Philosophy'',
René Descartes
René Descartes ( , ; ; 31 March 1596 – 11 February 1650) was a French philosopher, scientist, and mathematician, widely considered a seminal figure in the emergence of modern philosophy and Modern science, science. Mathematics was paramou ...
embarked upon a quest in which he called all his previous beliefs into doubt, to find out what he could be certain of.
In so doing, he discovered that he could doubt whether he had a body (it could be that he was dreaming of it or that it was an illusion created by an evil demon), but he could not doubt whether he had a mind. This gave Descartes his first inkling that the mind and body were different things. The mind, according to Descartes, was a "thinking thing" (), and an immaterial
substance. This "thing" was the essence of himself, that which doubts, believes, hopes, and thinks. The body, "the thing that exists" (), regulates normal bodily functions (such as heart and liver). According to Descartes, animals only had a body and not a soul (which distinguishes humans from animals). The distinction between mind and body is argued in ''Meditation'' VI as follows: I have a clear and distinct idea of myself as a thinking, non-extended thing, and a clear and distinct idea of body as an extended and non-thinking thing. Whatever I can conceive clearly and distinctly, God can so create.
The central claim of what is often called ''Cartesian dualism'', in honor of Descartes, is that the immaterial mind and the material body, while being ontologically distinct substances, causally interact. This is an idea that continues to feature prominently in many non-European philosophies. Mental events cause physical events, and vice versa. But this leads to a substantial problem for Cartesian dualism: How can an immaterial mind cause anything in a material body, and vice versa? This has often been called the "problem of interactionism."
Descartes himself struggled to come up with a feasible answer to this problem. In his letter to
Elisabeth of Bohemia, Princess Palatine, he suggested that spirits interacted with the body through the
pineal gland, a small gland in the centre of the brain, between the two
hemispheres.
The term ''Cartesian dualism'' is also often associated with this more specific notion of causal interaction through the pineal gland. However, this explanation was not satisfactory: ''how'' can an immaterial mind interact with the physical pineal gland? Because Descartes' was such a difficult theory to defend, some of his disciples, such as
Arnold Geulincx and
Nicolas Malebranche, proposed a different explanation: That all mind–body interactions required the direct intervention of God. According to these philosophers, the appropriate states of mind and body were only the ''occasions'' for such intervention, not real causes. These
occasionalists maintained the strong thesis that all causation was directly dependent on God, instead of holding that all causation was natural except for that between mind and body.
[ Schmaltz, Tad. 0022017.]
Nicolas Malebranche
" ''The Stanford Encyclopedia of Philosophy'', edited by E. N. Zalta.
Recent
In addition to already discussed theories of dualism (particularly the Christian and Cartesian models) there are new theories in the defense of dualism.
Naturalistic dualism comes from Australian philosopher,
David Chalmers (born 1966) who argues there is an explanatory gap between objective and subjective experience that cannot be bridged by reductionism because consciousness is, at least, logically autonomous of the physical properties upon which it supervenes. According to Chalmers, a naturalistic account of property dualism requires a new fundamental category of properties described by new laws of
supervenience; the challenge being analogous to that of understanding electricity based on the mechanistic and Newtonian models of materialism prior to
Maxwell's equations
Maxwell's equations, or Maxwell–Heaviside equations, are a set of coupled partial differential equations that, together with the Lorentz force law, form the foundation of classical electromagnetism, classical optics, Electrical network, electr ...
.
A similar defense comes from Australian philosopher
Frank Jackson (born 1943) who revived the theory of
epiphenomenalism which argues that mental states do not play a role in physical states. Jackson argues that there are two kinds of dualism:
# ''substance dualism'' that assumes there is second, non-corporeal form of reality. In this form, body and soul are two different substances.
# ''property dualism'' that says that body and soul are different ''properties'' of the same body.
He claims that functions of the mind/soul are internal, very private experiences that are not accessible to observation by others, and therefore not accessible by science (at least not yet). We can know everything, for example, about a bat's facility for echolocation, but we will never know how the bat experiences that phenomenon.
In 2018, ''The Blackwell Companion to Substance Dualism'' was published that contains arguments for and against Cartesian dualism, emergent dualism, Thomistic dualism, emergent individualism and nonreductive physicalism.
Contributors include
Charles Taliaferro, Edward Feser, William Hasker, J. P. Moreland, Richard Swinburne,
Lynne Rudder Baker, John W. Cooper and Timothy O'Connor.
Arguments for dualism
The subjective argument
An important fact is that minds perceive intra-mental states differently from sensory phenomena, and this cognitive difference results in mental and physical phenomena having seemingly disparate properties. The subjective argument holds that these properties are irreconcilable under a physical mind.
Mental events have a certain ''subjective'' quality to them, whereas physical ones seem not to. So, for example, one may ask what a burned finger feels like, or what the blueness of the sky looks like, or what nice music sounds like.
[ Nagel, Thomas. 1986. '' The View from Nowhere''. New York: Oxford University Press.] Philosophers of mind call the subjective aspects of mental events ''
qualia
In philosophy of mind, qualia (; singular: quale ) are defined as instances of subjective, conscious experience. The term ''qualia'' derives from the Latin neuter plural form (''qualia'') of the Latin adjective '' quālis'' () meaning "of what ...
.'' There is something ''that it's like'' to feel pain, to see a familiar shade of blue, and so on. There are ''qualia'' involved in these mental events. And the claim is that qualia cannot be reduced to anything physical.
Thomas Nagel first characterized the problem of qualia for physicalistic monism in his article, "
What Is It Like to Be a Bat?". Nagel argued that even if we knew everything there was to know from a third-person, scientific perspective about a bat's sonar system, we still wouldn't know what it is like to ''be'' a bat. However, others argue that ''qualia'' are consequent of the same neurological processes that engender the bat's mind, and will be fully understood as the
science
Science is a systematic discipline that builds and organises knowledge in the form of testable hypotheses and predictions about the universe. Modern science is typically divided into twoor threemajor branches: the natural sciences, which stu ...
develops.
Frank Jackson formulated his well-known ''
knowledge argument'' based upon similar considerations. In this
thought experiment
A thought experiment is an imaginary scenario that is meant to elucidate or test an argument or theory. It is often an experiment that would be hard, impossible, or unethical to actually perform. It can also be an abstract hypothetical that is ...
, known as
Mary's room, he asks us to consider a neuroscientist, Mary, who was born, and has lived all of her life, in a black and white room with a black and white television and computer monitor where she collects all the scientific data she possibly can on the nature of colours. Jackson asserts that as soon as Mary leaves the room, she will come to have new knowledge which she did not possess before: the knowledge of the experience of colours (i.e., what they are like). Although Mary knows everything there is to know about colours from an objective, third-person perspective, she has never known, according to Jackson, what it was like to see red, orange, or green. If Mary really learns something new, it must be knowledge of something non-physical, since she already knew everything about the physical aspects of colour.
However, Jackson later rejected his argument and embraced
physicalism. He notes that Mary obtains knowledge not of color, but of a new intramental state, ''seeing color''.
Also, he notes that Mary might say "wow," and as a mental state affecting the physical, this clashed with his former view of
epiphenomenalism.
David Lewis' response to this argument, now known as the ''ability'' argument, is that what Mary really came to know was simply the ability to recognize and identify color sensations to which she had previously not been exposed.
Daniel Dennett and others also provide
arguments against this notion.
The zombie argument
The
zombie argument is based on a
thought experiment
A thought experiment is an imaginary scenario that is meant to elucidate or test an argument or theory. It is often an experiment that would be hard, impossible, or unethical to actually perform. It can also be an abstract hypothetical that is ...
proposed by
David Chalmers over the issue of
qualia
In philosophy of mind, qualia (; singular: quale ) are defined as instances of subjective, conscious experience. The term ''qualia'' derives from the Latin neuter plural form (''qualia'') of the Latin adjective '' quālis'' () meaning "of what ...
or the
hard problem of consciousness. The basic idea is that one can imagine, and, therefore, conceive the existence of, an apparently functioning human being/body without any conscious states being associated with it.
Chalmers' argument is that it seems plausible that such a being could exist because all that is needed is that all and only the things that the physical sciences describe and observe about a human being must be true of the zombie. None of the concepts involved in these sciences make reference to consciousness or other mental phenomena, and any physical entity can be described scientifically via physics whether it is conscious or not. The mere logical possibility of a p-zombie demonstrates that consciousness is a natural phenomenon beyond the current unsatisfactory explanations. Chalmers states that one probably could not build a living p-zombie because living things seem to require a level of consciousness. However (unconscious?) robots built to simulate humans may become the first real p-zombies. Hence Chalmers half-joking calls for the need to build a "consciousness meter" to ascertain if any given entity, human or robot, is conscious or not.
Others such as Dennett have
argued that the notion of a philosophical zombie is an incoherent, or unlikely, concept. In particular, nothing proves that an entity (e.g., a computer or robot) which would perfectly mimic human beings, and especially perfectly mimic expressions of feelings (like joy, fear, anger, ...), would not indeed experience them, thus having similar states of consciousness to what a real human would have. It is argued that under
physicalism, one must either believe that anyone including oneself might be a zombie, or that no one can be a zombie—following from the assertion that one's own conviction about being (or not being) a zombie is a product of the physical world and is therefore no different from anyone else's.
Avshalom Elitzur has described himself as a "reluctant dualist". One argument Elitzur makes in favor of dualism is an argument from bafflement. According to Elitzur, a conscious being can conceive of a P-zombie version of his/herself. However, a P-zombie cannot conceive of a version of itself that lacks corresponding qualia.
Special sciences argument
Howard Robinson argues that, if predicate dualism is correct, then there are "special sciences" that are irreducible to physics. These allegedly irreducible subjects, which contain irreducible predicates, differ from hard sciences in that they are interest-relative. Here, interest-relative fields depend on the existence of minds that can have interested perspectives.
Psychology is one such science; it completely depends on and presupposes the existence of the mind.
Physics is the general analysis of
nature
Nature is an inherent character or constitution, particularly of the Ecosphere (planetary), ecosphere or the universe as a whole. In this general sense nature refers to the Scientific law, laws, elements and phenomenon, phenomena of the physic ...
, conducted to understand how the
universe
The universe is all of space and time and their contents. It comprises all of existence, any fundamental interaction, physical process and physical constant, and therefore all forms of matter and energy, and the structures they form, from s ...
behaves. On the other hand, the study of
meteorological weather patterns or
human behavior
Human behavior is the potential and expressed capacity (Energy (psychological), mentally, Physical activity, physically, and Social action, socially) of human individuals or groups to respond to internal and external Stimulation, stimuli throu ...
is only of interest to humans themselves. The point is that having a perspective on the world is a psychological state. Therefore, the special sciences presuppose the existence of minds which can have these states. If one is to avoid ontological dualism, then the mind that ''has'' a perspective must be part of the physical reality to which it ''applies'' its perspective. If this is the case, then to perceive the physical world as psychological, the mind must have a perspective on the physical. This, in turn, presupposes the existence of mind.
However,
cognitive science
Cognitive science is the interdisciplinary, scientific study of the mind and its processes. It examines the nature, the tasks, and the functions of cognition (in a broad sense). Mental faculties of concern to cognitive scientists include percep ...
and psychology do not require the mind to be irreducible, and operate on the assumption that it has physical basis. In fact, it is common in science to presuppose a complex system;
while fields such as
chemistry
Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...
,
biology
Biology is the scientific study of life and living organisms. It is a broad natural science that encompasses a wide range of fields and unifying principles that explain the structure, function, growth, History of life, origin, evolution, and ...
, or geology could be verbosely expressed in terms of
quantum field theory
In theoretical physics, quantum field theory (QFT) is a theoretical framework that combines Field theory (physics), field theory and the principle of relativity with ideas behind quantum mechanics. QFT is used in particle physics to construct phy ...
, it is convenient to use levels of abstraction like
molecules
A molecule is a group of two or more atoms that are held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemistry ...
,
cells, or the
mantle. It is often difficult to decompose these levels without heavy analysis and computation. Sober has also advanced philosophical arguments against the notion of irreducibility.
Argument from personal identity
This argument concerns the differences between the applicability of
counterfactual conditionals to physical objects, on the one hand, and to conscious, personal agents on the other.
[Madell, G. 1981. ''The Identity of the Self''. Edinburgh: Edinburgh University Press.] In the case of any material object, e.g. a printer, we can formulate a series of counterfactuals in the following manner:
# This printer could have been made of straw.
# This printer could have been made of some other kind of plastics and vacuum-tube transistors.
# This printer could have been made of 95% of what it is actually made of and 5% vacuum-tube transistors, etc..
Somewhere along the way from the printer's being made up exactly of the parts and materials which actually constitute it to the printer's being made up of some different matter at, say, 20%, the question of whether this printer is the same printer becomes a matter of arbitrary convention.
Imagine the case of a person, Frederick, who has a counterpart born from the same egg and a slightly
genetically modified sperm. Imagine a series of counterfactual cases corresponding to the examples applied to the printer. Somewhere along the way, one is no longer sure about the identity of Frederick. In this latter case, it has been claimed, ''overlap of constitution'' cannot be applied to the identity of mind. As Madell puts it:
:But while my present body can thus have its partial counterpart in some possible world, my present consciousness cannot. Any present state of consciousness that I can imagine either is or is not mine. There is no question of degree here.
If the counterpart of Frederick, Frederickus, is 70% constituted of the same physical substance as Frederick, does this mean that it is also 70% mentally identical with Frederick? Does it make sense to say that something is mentally 70% Frederick? A possible solution to this dilemma is that of
open individualism.
Richard Swinburne, in his book ''The Existence of God'', put forward an argument for mind-body dualism based upon personal identity. He states that the brain is composed of two hemispheres and a cord linking the two and that, as modern science has shown, either of these can be removed without the person losing any memories or mental capacities.
He then cites a thought-experiment for the reader, asking what would happen if each of the two hemispheres of one person were placed inside two different people. Either, Swinburne claims, one of the two is me or neither is—and there is no way of telling which, as each will have similar memories and mental capacities to the other. In fact, Swinburne claims, even if one's mental capacities and memories are far more similar to the original person than the others' are, they still may not be him.
From here, he deduces that even if we know what has happened to every single atom inside a person's brain, we still do not know what has happened to 'them' as an identity. From here it follows that a part of our mind, or our soul, is immaterial, and, as a consequence, that mind-body dualism is true.
[ Swinburne, Richard. 1979. ''The Existence of God''. Oxford: Oxford University Press.]
Christian List
Christian List (born 1973) is a German philosopher and political scientist who serves as professor of philosophy and decision theory at the Ludwig Maximilian University of Munich and co-director of the Munich Center for Mathematical Philosop ...
argues that Benj Hellie's
vertiginous question, i.e. why people exist as themselves and not as someone else, and the existence of first-personal facts, are a refutation of physicalist philosophies of consciousness. List argues that first personal facts cannot supervene on third personal facts. However, List also argues that this also refutes standard versions of mind-body dualism that have purely third-personal metaphysics.
Argument from reason
Philosophers and scientists such as
Victor Reppert,
William Hasker, and
Alvin Plantinga
Alvin Carl Plantinga (born November 15, 1932) is an American analytic philosophy, analytic philosopher who works primarily in the fields of philosophy of religion, epistemology (particularly on issues involving theory of justification, epistemic ...
have developed an argument for dualism dubbed the "argument from reason". They credit
C. S. Lewis
Clive Staples Lewis (29 November 1898 – 22 November 1963) was a British writer, literary scholar and Anglican lay theologian. He held academic positions in English literature at both Magdalen College, Oxford (1925–1954), and Magdalen ...
with first bringing the argument to light in his book ''
Miracles''; Lewis called the argument "The Cardinal Difficulty of Naturalism", which was the title of chapter three of ''Miracles''.
[ Reppert, Victor. 2003. ''C.S. Lewis's Dangerous Idea''. Downers Grove, IL: InterVarsity Press. ]
The argument postulates that if, as naturalism entails, all of our thoughts are the effect of a physical cause, then we have no reason for assuming that they are also the consequent of a reasonable ground. However, knowledge is apprehended by reasoning from ground to consequent. Therefore, if naturalism were true, there would be no way of knowing it (or anything else), except by a fluke.
Through this logic, the statement "I have reason to believe naturalism is valid" is inconsistent in the same manner as "I never tell the truth." That is, to conclude its truth would eliminate the grounds from which to reach it. To summarize the argument in the book, Lewis quotes
J. B. S. Haldane, who appeals to a similar line of reasoning:
In his essay "Is Theology Poetry?", Lewis himself summarises the argument in a similar fashion when he writes:
But Lewis later agreed with
Elizabeth Anscombe's response to his ''Miracles'' argument. She showed that an argument could be valid and ground-consequent even if its propositions were generated via
physical cause and effect by non-rational factors. Similar to Anscombe,
Richard Carrier and John Beversluis have written extensive objections to the
argument from reason on the untenability of its first postulate.
Cartesian arguments
Descartes puts forward two main arguments for dualism in ''
Meditations
''Meditations'' () is a series of personal writings by Marcus Aurelius, Roman Emperor from 161–180 AD, recording his private notes to himself and ideas on Stoic philosophy. Composition
Marcus Aurelius wrote the 12 books of the ''Meditations'' i ...
'': firstly, the "modal argument," or the "clear and distinct perception argument," and secondly the "indivisibility" or "divisibility" argument.
The argument is distinguished from the
Zombie Argument as it establishes that the mind could continue to exist without the body, rather than that the unaltered body could exist without the mind.
Alvin Plantinga
Alvin Carl Plantinga (born November 15, 1932) is an American analytic philosophy, analytic philosopher who works primarily in the fields of philosophy of religion, epistemology (particularly on issues involving theory of justification, epistemic ...
,
J. P. Moreland, and
Edward Feser have both supported the argument, although Feser and Moreland think that it must be carefully reformulated to be effective.
The ''indivisibility argument'' for dualism was phrased by Descartes as follows:
ere is a great difference between a mind and a body, because the body, by its very nature, is something divisible, whereas the mind is plainly indivisible...insofar as I am only a thing that thinks, I cannot distinguish any parts in me.... Although the whole mind seems to be united to the whole body, nevertheless, were a foot or an arm or any other bodily part amputated, I know that nothing would be taken away from the mind...
The argument relies upon
Leibniz'
principle of the identity of indiscernibles, which states that two things are the same if and only if they share all their properties. A counterargument is the idea that matter is not infinitely divisible, and thus that the mind could be identified with material things that cannot be divided, or potentially Leibnizian
monads.
Arguments against dualism
Arguments from causal interaction

One argument against dualism is with regard to causal interaction. If consciousness (''the mind'') can exist independently of physical reality (''the brain''), one must explain how physical memories are created concerning consciousness. Dualism must therefore explain how consciousness affects physical reality. One of the main objections to dualistic interactionism is lack of explanation of how the material and immaterial are able to interact. Varieties of dualism according to which an immaterial mind causally affects the material body and vice versa have come under strenuous attack from different quarters, especially in the 20th century. Critics of dualism have often asked how something totally immaterial can affect something totally material—this is the basic problem of causal interaction.
First, it is not clear ''where'' the interaction would take place. For example, burning one's finger causes pain. Apparently there is some chain of events, leading from the burning of skin, to the stimulation of nerve endings, to something happening in the peripheral nerves of one's body that lead to one's brain, to something happening in a particular part of one's brain, and finally resulting in the sensation of pain. But pain is not supposed to be spatially locatable. It might be responded that the pain "takes place in the brain." But evidently, the pain is in the finger. This may not be a devastating criticism.
However, there is a second problem about the interaction. Namely, the question of ''how'' the interaction takes place, where in dualism "the mind" is assumed to be non-physical and by definition outside of the realm of science. The ''mechanism'' which explains the connection between the mental and the physical would therefore be a philosophical proposition as compared to a scientific theory. For example, compare such a mechanism to a physical mechanism that ''is'' well understood. Take a very simple causal relation, such as when a cue ball strikes an eight ball and causes it to go into the pocket. What happens in this case is that the cue ball has a certain amount of momentum as its mass moves across the pool table with a certain velocity, and then that momentum is transferred to the eight ball, which then heads toward the pocket. Compare this to the situation in the brain, where one wants to say that a decision causes some neurons to fire and thus causes a body to move across the room. The intention to "cross the room now" is a mental event and, as such, it does not have physical properties such as force. If it has no force, then it would seem that it could not possibly cause any neuron to fire. However, with Dualism, an explanation is required of how something without any physical properties has physical ''effects''.
Replies
Alfred North Whitehead
Alfred North Whitehead (15 February 1861 – 30 December 1947) was an English mathematician and philosopher. He created the philosophical school known as process philosophy, which has been applied in a wide variety of disciplines, inclu ...
, and later
David Ray Griffin, framed a new ontology (''
process philosophy'') seeking precisely to avoid the pitfalls of ontological dualism.
The explanation provided by
Arnold Geulincx and
Nicolas Malebranche is that of
occasionalism, where all mind–body interactions require the direct intervention of God.
At the time
C. S. Lewis
Clive Staples Lewis (29 November 1898 – 22 November 1963) was a British writer, literary scholar and Anglican lay theologian. He held academic positions in English literature at both Magdalen College, Oxford (1925–1954), and Magdalen ...
wrote ''
Miracles'',
quantum mechanics
Quantum mechanics is the fundamental physical Scientific theory, theory that describes the behavior of matter and of light; its unusual characteristics typically occur at and below the scale of atoms. Reprinted, Addison-Wesley, 1989, It is ...
(and physical
indeterminism
Indeterminism is the idea that events (or certain events, or events of certain types) are not caused, or are not caused deterministically.
It is the opposite of determinism and related to chance. It is highly relevant to the philosophical pr ...
) was only in the initial stages of acceptance, but still Lewis stated the logical possibility that, if the physical world was proved to be indeterministic, this would provide an entry (interaction) point into the traditionally viewed closed system, where a scientifically described physically probable/improbable event could be philosophically described as an action of a non-physical entity on physical reality. He states, however, that none of the arguments in his book will rely on this. Although some
interpretations of quantum mechanics consider
wave function collapse to be indeterminate, in others this event is defined as deterministic.
Argument from physics
The argument from physics is closely related to the argument from causal interaction. Many physicists and consciousness researchers have argued that any action of a nonphysical mind on the brain would entail the violation of physical laws, such as the
conservation of energy.
By assuming a deterministic physical universe, the objection can be formulated more precisely. When a person decides to walk across a room, it is generally understood that the decision to do so, a mental event, immediately causes a group of neurons in that person's brain to fire, a physical event, which ultimately results in his walking across the room. The problem is that if there is something totally non-physical ''causing'' a bunch of neurons to fire, then there is no ''physical'' event which causes the firing. This means that some physical energy is required to be generated against the physical laws of the deterministic universe—this is by definition a miracle and there can be no scientific explanation of (repeatable experiment performed regarding) where the ''physical'' energy for the firing came from. Such interactions would violate the fundamental
laws of physics. In particular, if some external source of energy is responsible for the interactions, then this would violate the law of the
conservation of energy. Dualistic interactionism has therefore been criticized for violating a general
heuristic principle of science: the
causal closure
Physical causal closure is a metaphysical theory about the nature of causation in the physical realm with significant ramifications in the study of metaphysics and the mind. In a strongly stated version, physical causal closure says that "all phy ...
of the physical world.
Replies
The ''
Stanford Encyclopedia of Philosophy
The ''Stanford Encyclopedia of Philosophy'' (''SEP'') is a freely available online philosophy resource published and maintained by Stanford University, encompassing both an online encyclopedia of philosophy and peer-reviewed original publication ...
''
and the ''
New Catholic Encyclopedia''
[Maher, Michael (1909) "The Law of Conservation of Energy", ''Catholic Encyclopedia'', vol. 5, pp. 422 ff, .] provide two possible replies to the above objections. The first reply is that the mind may influence the ''distribution'' of energy, without altering its quantity. The second possibility is to deny that the human body is causally closed, as the
conservation of energy applies only to closed systems. However, physicalists object that no evidence exists for the causal non-closure of the human body.
Robin Collins responds that energy conservation objections misunderstand the role of energy conservation in physics. Well understood scenarios in general relativity violate energy conservation and quantum mechanics provides precedent for causal interactions, or correlation without energy or momentum exchange. However, this does not mean the mind spends energy and, despite that, it still doesn't exclude the supernatural.
Another reply is akin to parallelism—Mills holds that behavioral events are causally
overdetermined, and can be explained by either physical or mental causes alone. An overdetermined event is fully accounted for by multiple causes at once. However,
J. J. C. Smart and
Paul Churchland have pointed out that if physical phenomena fully determine behavioral events, then by
Occam's razor an unphysical mind is unnecessary.
Howard Robinson suggests that the interaction may involve
dark energy
In physical cosmology and astronomy, dark energy is a proposed form of energy that affects the universe on the largest scales. Its primary effect is to drive the accelerating expansion of the universe. It also slows the rate of structure format ...
,
dark matter
In astronomy, dark matter is an invisible and hypothetical form of matter that does not interact with light or other electromagnetic radiation. Dark matter is implied by gravity, gravitational effects that cannot be explained by general relat ...
or some other currently unknown scientific process.
Another reply is that the interaction taking place in the human body may not be described by "billiard ball"
classical mechanics
Classical mechanics is a Theoretical physics, physical theory describing the motion of objects such as projectiles, parts of Machine (mechanical), machinery, spacecraft, planets, stars, and galaxies. The development of classical mechanics inv ...
. If a nondeterministic interpretation of
quantum mechanics
Quantum mechanics is the fundamental physical Scientific theory, theory that describes the behavior of matter and of light; its unusual characteristics typically occur at and below the scale of atoms. Reprinted, Addison-Wesley, 1989, It is ...
is correct then microscopic events are
indeterminate, where the degree of
determinism
Determinism is the Metaphysics, metaphysical view that all events within the universe (or multiverse) can occur only in one possible way. Deterministic theories throughout the history of philosophy have developed from diverse and sometimes ov ...
increases with the scale of the system. Philosophers
Karl Popper
Sir Karl Raimund Popper (28 July 1902 – 17 September 1994) was an Austrian–British philosopher, academic and social commentator. One of the 20th century's most influential philosophers of science, Popper is known for his rejection of the ...
and
John Eccles and physicist
Henry Stapp have theorized that such indeterminacy may apply at the macroscopic scale. However,
Max Tegmark has argued that classical and quantum calculations show that
quantum decoherence effects do not play a role in brain activity.
Yet another reply to the interaction problem is to note that it doesn't seem that there is an interaction problem for all forms of substance dualism. For instance,
Thomistic dualism doesn't obviously face any issue with regards to interaction, for in this view the soul and the body are related as form and matter.
Argument from brain damage
This argument has been formulated by
Paul Churchland, among others. The point is that, in instances of some sort of brain damage (e.g. caused by automobile accidents, drug abuse, pathological diseases, etc.), it is always the case that the mental substance and/or properties of the person are significantly changed or compromised. If the mind were a completely separate substance from the brain, how could it be possible that every single time the brain is injured, the mind is also injured? Indeed, it is very frequently the case that one can even predict and explain the kind of mental or psychological deterioration or change that human beings will undergo when specific parts of their brains are damaged. So the question for the dualist to try to confront is how can all of this be explained if the mind is a separate and immaterial substance from, or if its properties are ontologically independent of, the brain.
Phineas Gage, who suffered destruction of one or both frontal lobes by a projectile iron rod, is often cited as an example illustrating that the brain causes mind. Gage certainly exhibited some mental changes after his accident, suggesting a correlation between brain states and mental states. It has been noted, however, that Gage's most serious mental changes were only temporary, and that he made a reasonable social and mental recovery. The changes in question have almost always been distorted and exaggerated by scientific and popular literature, often relying on hearsay. Similar examples abound; neuroscientist
David Eagleman describes the case of another individual who exhibited escalating
pedophilic tendencies at two different times, and in each case was found to have tumors growing in a particular part of his brain.
Case studies aside, modern experiments have demonstrated that the relation between brain and mind is much more than simple correlation. By damaging, or manipulating, specific areas of the brain repeatedly under controlled conditions (e.g. in monkeys) and reliably obtaining the same results in measures of mental state and abilities, neuroscientists have shown that the relation between damage to the brain and mental deterioration is likely causal. This conclusion is further supported by data from the effects of neuro-active chemicals (e.g., those affecting
neurotransmitters) on mental functions, but also from research on
neurostimulation (direct electrical stimulation of the brain, including
transcranial magnetic stimulation).
Replies
Property dualism and
William Hasker's "emergent dualism" seek to avoid this problem. They assert that the mind is a property or substance that emerges from the appropriate arrangement of physical matter, and therefore could be affected by any rearrangement of matter.
Writing in the 13th century, St.
Thomas Aquinas
Thomas Aquinas ( ; ; – 7 March 1274) was an Italian Dominican Order, Dominican friar and Catholic priest, priest, the foremost Scholasticism, Scholastic thinker, as well as one of the most influential philosophers and theologians in the W ...
writes that "the body is necessary for the action of the intellect, not as origin of action." Thus, if the body is dysfunctional, the intellect will not actualize as it intends to. According to the philosopher
Stephen Evans:
Argument from neuroscience
In some contexts, the decisions that a person makes can be detected up to 10 seconds in advance by means of scanning their brain activity. Subjective experiences and covert attitudes can be detected,
as can mental imagery. This is strong
empirical evidence
Empirical evidence is evidence obtained through sense experience or experimental procedure. It is of central importance to the sciences and plays a role in various other fields, like epistemology and law.
There is no general agreement on how the ...
that
cognitive processes have a physical basis in the brain.
Argument from simplicity
The argument from simplicity is probably the simplest and also the most common form of argument against dualism of the mental. The dualist is always faced with the question of why anyone should find it necessary to believe in the existence of two, ontologically distinct, entities (mind and brain), when it seems possible and would make for a simpler thesis to test against scientific evidence, to explain the same events and properties in terms of one. It is a heuristic principle in science and philosophy not to assume the existence of more entities than is necessary for clear explanation and prediction.
This argument was criticized by
Peter Glassen in a debate with
J. J. C. Smart in the pages of ''
Philosophy
Philosophy ('love of wisdom' in Ancient Greek) is a systematic study of general and fundamental questions concerning topics like existence, reason, knowledge, Value (ethics and social sciences), value, mind, and language. It is a rational an ...
'' in the late 1970s and early 1980s.
Glassen argued that, because it is not a physical entity,
Occam's razor cannot consistently be appealed to by a physicalist or materialist as a justification of mental states or events, such as the belief that dualism is false. The idea is that Occam's razor may not be as "unrestricted" as it is normally described (applying to all qualitative postulates, even abstract ones) but instead concrete (only applies to physical objects). If one applies Occam's Razor unrestrictedly, then it recommends monism until pluralism either receives more support or is disproved. If one applies Occam's Razor only concretely, then it may not be used on abstract concepts (this route, however, has serious consequences for selecting between hypotheses ''about'' the abstract).
[Plato Stanford Encyclopedia of Philosophy: Simplicity]
Excerpt: "Perhaps scientists apply an unrestricted version of Occam's Razor to that portion of reality in which they are interested, namely the concrete, causal, spatiotemporal world. Or perhaps scientists apply a 'concretized' version of Occam's Razor unrestrictedly. Which is the case? The answer determines which general philosophical principle we end up with: ought we to avoid the multiplication of objects of whatever kind, or merely the multiplication of concrete objects? The distinction here is crucial for a number of central philosophical debates. Unrestricted Occam's Razor favors monism over dualism, and nominalism over platonism. By contrast, 'concretized' Occam's Razor has no bearing on these debates, since the extra entities in each case are not concrete".
This argument has also been criticized by Seyyed Jaaber Mousavirad, who argues that the principle of simplicity could only be applied when there is no need for an additional entity. Despite arguments indicating the need for the soul, the principle of simplicity does not apply. Therefore, if there were no argument establishing the existence of the soul, one could deny its existence based on the principle of simplicity. However, various arguments have been put forth to establish its existence. These arguments demonstrate that while neuroscience can explain the mysteries of the material brain, certain significant issues, such as personal identity and free will, remain beyond the scope of neuroscience. The crux of the matter lies in the essential limitations of neuroscience and the potency of substance dualism in explaining these phenomena.
See also
*
Explanatory gap
*
Mentalism (psychology)
*
Nondualism
*
Hard problem of consciousness
*
Bipartite (theology)
* ''
The Concept of Mind'' by
Gilbert Ryle
*
Trialism
*
Vertiginous question
References
Further reading
* Amoroso, Richard L. 2010. ''Complementarity of Mind and Body: Realizing the Dream of Descartes, Einstein and Eccles''. . History making volume with first comprehensive model of dualism-interactionism, that is also empirically testable.
* Bracken, Patrick, and Philip Thomas. 2002. "Time to move beyond the mind–body split." ''
British Medical Journal'' 325:1433–1434. . A controversial perspective on the use and possible overuse of the Mind–Body split and its application in medical practice.
*
Damasio, Antonio. 1994. ''
Descartes' Error''.
* Sinclair, Alistair J. 2015. ''The Promise of Dualism''. Almostic Publications. . Introducing dualism as being interactive and distinct from the substance dualism of Descartes.
* Spenard, Michael. 2011. . . An historical account of mind body dualism and a comprehensive conceptual and an empirical critique of the position.
* Sperry, R. W. 1980. "Mind-brain interaction: Mentalism, yes; dualism, no." ''
Neuroscience
Neuroscience is the scientific study of the nervous system (the brain, spinal cord, and peripheral nervous system), its functions, and its disorders. It is a multidisciplinary science that combines physiology, anatomy, molecular biology, ...
'' 5(2):195–206. . .
External links
*
*
Dualism" ''Dictionary of Philosophy of Mind''
*
Dualism" the ''
Stanford Encyclopedia of Philosophy
The ''Stanford Encyclopedia of Philosophy'' (''SEP'') is a freely available online philosophy resource published and maintained by Stanford University, encompassing both an online encyclopedia of philosophy and peer-reviewed original publication ...
''
*
Zombies" ''Stanford Encyclopedia of Philosophy''
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Dualism Arguments: Pros & Cons
{{DEFAULTSORT:Mind-body dualism
Arguments in philosophy of mind
Baruch Spinoza
Cartesianism
Concepts in epistemology
Concepts in metaphysics
Concepts in the philosophy of mind
Consciousness
Metaphysics of mind
Ontology
René Descartes
Theory of mind