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The is–ought problem, as articulated by the Scottish
philosopher 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 ...
and
historian A historian is a person who studies and writes about the past and is regarded as an authority on it. Historians are concerned with the continuous, methodical narrative and research of past events as relating to the human species; as well as the ...
David Hume David Hume (; born David Home; – 25 August 1776) was a Scottish philosopher, historian, economist, and essayist who was best known for his highly influential system of empiricism, philosophical scepticism and metaphysical naturalism. Beg ...
, arises when one makes claims about what ''ought'' to be that are based solely on statements about what ''is''. Hume found that there seems to be a significant difference between descriptive statements (about what is) and prescriptive statements (about what ought to be), and that it is not obvious how one can coherently transition from descriptive statements to prescriptive ones. Hume's law or Hume's guillotine is the thesis that an
ethical Ethics is the philosophical study of moral phenomena. Also called moral philosophy, it investigates normative questions about what people ought to do or which behavior is morally right. Its main branches include normative ethics, applied e ...
or judgmental conclusion cannot be inferred from purely descriptive factual statements. A similar view is defended by
G. E. Moore George Edward Moore (4 November 1873 – 24 October 1958) was an English philosopher, who with Bertrand Russell, Ludwig Wittgenstein and earlier Gottlob Frege was among the initiators of analytic philosophy. He and Russell began de-emphasizing ...
's open-question argument, intended to refute any identification of
moral A moral (from Latin ''morālis'') is a message that is conveyed or a lesson to be learned from a story or event. The moral may be left to the hearer, reader, or viewer to determine for themselves, or may be explicitly encapsulated in a maxim. ...
properties with natural
properties Property is the ownership of land, resources, improvements or other tangible objects, or intellectual property. Property may also refer to: Philosophy and science * Property (philosophy), in philosophy and logic, an abstraction characterizing an ...
, which is asserted by ethical naturalists, who do not deem the naturalistic fallacy a fallacy. The is–ought problem is closely related to the
fact–value distinction The fact–value distinction is a fundamental epistemological distinction described between: # Statements of fact (positive or descriptive statements), which are based upon reason and observation, and examined via the empirical method. # Statem ...
in
epistemology Epistemology is the branch of philosophy that examines the nature, origin, and limits of knowledge. Also called "the theory of knowledge", it explores different types of knowledge, such as propositional knowledge about facts, practical knowle ...
. Though the terms are often used interchangeably, academic discourse concerning the latter may encompass
aesthetics Aesthetics (also spelled esthetics) is the branch of philosophy concerned with the nature of beauty and taste (sociology), taste, which in a broad sense incorporates the philosophy of art.Slater, B. H.Aesthetics ''Internet Encyclopedia of Ph ...
in addition to
ethics Ethics is the philosophy, philosophical study of Morality, moral phenomena. Also called moral philosophy, it investigates Normativity, normative questions about what people ought to do or which behavior is morally right. Its main branches inclu ...
.


Overview

Hume discusses the problem in book III, part I, section I of his book, '' A Treatise of Human Nature'' (1739): Hume calls for caution against such inferences in the absence of any explanation of how the ought-statements follow from the is-statements. But how exactly ''can'' an "ought" be derived from an "is"? The question, prompted by Hume's small paragraph, has become one of the central questions of ethical theory, and Hume is usually assigned the position that such a derivation is impossible. In modern times, "Hume's law" often denotes the informal thesis that, if a reasoner only has access to non-moral factual premises, the reasoner cannot logically infer the truth of moral statements; or, more broadly, that one cannot infer evaluative statements (including aesthetic statements) from non-evaluative statements. An alternative definition of Hume's law is that "If P implies Q, and Q is moral, then P is moral". This interpretation-driven definition avoids a loophole with the principle of explosion. Other versions state that the is–ought gap can technically be formally bridged without a moral premise, but only in ways that are formally "vacuous" or "irrelevant", and that provide no "guidance". For example, one can infer from "The Sun is yellow" that "Either the Sun is yellow, or it is wrong to murder". But this provides no relevant moral guidance; absent a contradiction, one cannot deductively infer that "it is wrong to murder" solely from non-moral premises alone, adherents argue.


Implications

The apparent gap between "is" statements and "ought" statements, when combined with Hume's fork, renders "ought" statements of dubious validity. Hume's fork is the idea that all items of knowledge are based either on logic and definitions, or else on observation. If the is–ought problem holds, then "ought" statements do not seem to be known in either of these two ways, and it would seem that there can be no moral knowledge.
Moral skepticism Moral skepticism (or moral scepticism in British English) is a class of meta-ethical theories all members of which entail that no one has any moral knowledge. Many moral skeptics also make the stronger, modal claim that moral knowledge is i ...
and
non-cognitivism Non-cognitivism is the meta-ethical view that ethical sentences do not express propositions (i.e., statements) and thus cannot be true or false (they are not truth-apt). A noncognitivist denies the cognitivist claim that "moral judgments are ...
work with such conclusions.


Responses


Oughts and goals

Ethical naturalists contend that moral truths exist, and that their truth value relates to facts about physical reality. Many modern naturalistic philosophers see no impenetrable barrier in deriving "ought" from "is", believing it can be done whenever we analyze goal-directed behavior. They suggest that a statement of the form ''"In order for agent ''A'' to achieve goal ''B'', ''A'' reasonably ought to do ''C''"'' exhibits no category error and may be factually verified or refuted. "Oughts" exist, then, in light of the existence of goals. A counterargument to this response is that it merely pushes back the "ought" to the subjectively valued "goal" and thus provides no fundamentally objective basis to one's goals which, consequentially, provides no basis of distinguishing moral value of fundamentally different goals. A dialectical naturalist response to this objection is that although it is true that individual goals have a degree of subjectivity, the process through which the existence of goals is made possible is not subjective—that is, the advent of organisms capable of subjectivity, having occurred through the objective process of
evolution Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...
. This dialectical approach goes further to state that subjectivity should be conceptualized as objectivity at its highest point, having been the result of an unfolding developmental process. This is similar to work done by the moral philosopher
Alasdair MacIntyre Alasdair Chalmers MacIntyre (12 January 1929 – 21 May 2025) was a Scottish-American philosopher who contributed to moral and political philosophy as well as history of philosophy and theology. MacIntyre's '' After Virtue'' (1981) is one of ...
, who attempts to show that because ethical language developed in the West in the context of a belief in a human
telos Telos (; ) is a term used by philosopher Aristotle to refer to the final cause of a natural organ or entity, or of human art. ''Telos'' is the root of the modern term teleology, the study of purposiveness or of objects with a view to their aims, ...
—an end or goal—our inherited moral language, including terms such as good and bad, have functioned, and function, to evaluate the way in which certain behaviors facilitate the achievement of that telos. In an evaluative capacity, therefore, good and bad carry moral weight without committing a category error. For instance, a pair of scissors that cannot easily cut through paper can legitimately be called bad since it cannot fulfill its purpose effectively. Likewise, if a person is understood as having a particular purpose, then behaviour can be evaluated as good or bad in reference to that purpose. In plainer words, a person is acting good when that person fulfills that person's purpose. Even if the concept of an "ought" is meaningful, this need not involve morality. This is because some goals may be morally neutral, or (if they exist) against what is moral. A poisoner might realize his victim has not died and say, for example, "I ought to have used more poison," since his goal is to murder. The next challenge of a moral realist is thus to explain what is meant by a "''moral'' ought".


Discourse ethics

Proponents of discourse ethics argue that the very act of discourse implies certain "oughts", that is, certain
presupposition In linguistics and philosophy, a presupposition is an implicit assumption about the world or background belief relating to an utterance whose truth is taken for granted in discourse. Examples of presuppositions include: * ''Jane no longer writes ...
s that are necessarily accepted by the participants in discourse, and can be used to further derive prescriptive statements. They therefore argue that it is incoherent to argumentatively advance an ethical position on the basis of the is–ought problem, which contradicts these implied assumptions.


Moral oughts

As MacIntyre explained, someone may be called a good person if people have an inherent purpose. Many ethical systems appeal to such a purpose. This is true of some forms of moral realism, which states that something can be wrong, even if every thinking person ''believes'' otherwise (the idea of
brute fact In contemporary philosophy, a brute fact is a fact that cannot be explained in terms of a deeper, more "fundamental" fact. There are two main ways to explain something: say what "brought it about", or describe it at a more "fundamental" level. For ...
about morality). The ethical realist might suggest that humans were created for a purpose (e.g. to serve God), especially if they are an ethical non-naturalist. If the ethical realist is instead an ethical naturalist, they may start with the fact that humans have evolved and pursue some sort of evolutionary ethics (which risks “committing” the moralistic fallacy). Not all moral systems appeal to a human telos or purpose. This is because it is not obvious that people even ''have'' any sort of natural purpose, or what that purpose would be. Although many scientists do recognize teleonomy (a tendency in nature), few philosophers appeal to it (this time, to avoid the naturalistic fallacy). Goal-dependent oughts run into problems even without an appeal to an innate human purpose. Consider cases where one has no desire to be good—whatever it is. If, for instance, a person wants to be good, and good means washing one's hands, then it seems one morally ought to wash their hands. The bigger problem in moral philosophy is what happens if someone does ''not'' want to be good, whatever its origins? Put simply, in what sense ''ought'' we to hold the goal of being good? It seems one can ask "how am I rationally required to hold 'good' as a value, or to pursue it?" The issue above mentioned is a result of an important ethical relativist critique. Even if "oughts" depend on goals, the ought seems to vary with the person's goal. This is the conclusion of the ethical subjectivist, who says a person can only be called good according to whether they fulfill their own, ''self-assigned'' goal. Alasdair MacIntyre himself suggests that a person's purpose comes from their culture, making him a sort of ethical relativist. Ethical relativists acknowledge local, institutional facts about what is right, but these are facts that can still vary by society. Thus, without an objective "moral goal", a moral ought is difficult to establish.
G. E. M. Anscombe Gertrude Elizabeth Margaret Anscombe (; 18 March 1919 – 5 January 2001), usually cited as G. E. M. Anscombe or Elizabeth Anscombe, was a British analytic philosopher. She wrote on the philosophy of mind, philosophy of action, philosophi ...
was particularly critical of the word "ought" for this reason; understood as "We need such-and-such, and will only get it this way"for somebody may need something immoral, or else find that their noble need requires immoral action. Anscombe would even go as far to suggest that "the concepts of obligation, and duty''moral'' obligation and ''moral'' duty, that is to sayand of what is ''morally'' right and wrong, and of the ''moral'' sense of 'ought,' ought to be jettisoned if this is psychologically possible". If moral goals depend on private assumptions or public agreement, so may morality as a whole. For example, Canada might call it good to maximize global welfare, where a citizen, Alice, calls it good to focus on herself, and then her family, and finally her friends (with little empathy for strangers). It does not seem that Alice can be objectively or rationally bound—without regard to her personal values ''nor'' those of groups of other people—to act a certain way. In other words, we may not be able to say "You just ''should'' do this". Moreover, persuading her to help strangers would necessarily mean appealing to values she already possesses (or else we would never even have a hope of persuading her). This is another interest of
normative ethics Normative ethics is the study of ethics, ethical behaviour and is the branch of Philosophy, philosophical ethics that investigates questions regarding how one ought to act, in a Morality, moral sense. Normative ethics is distinct from metaethics i ...
—questions of binding forces. There may be responses to the above relativistic critiques. As mentioned above, ethical realists that are non-natural can appeal to God's purpose for humankind. On the other hand, naturalistic thinkers may posit that valuing people's well-being is somehow "obviously" the purpose of ethics, or else the only relevant purpose worth talking about. This is the move made by
natural law Natural law (, ) is a Philosophy, philosophical and legal theory that posits the existence of a set of inherent laws derived from nature and universal moral principles, which are discoverable through reason. In ethics, natural law theory asserts ...
, scientific moralists and some utilitarians.


Institutional facts

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 ...
also attempts to derive "ought" from "is". He tries to show that the act of making a promise places one under an obligation by definition, and that such an obligation amounts to an "ought". This view is still widely debated, and to answer criticisms, Searle has further developed the concept of
institutional fact In contemporary philosophy, a brute fact is a fact that cannot be explained in terms of a deeper, more "fundamental" fact. There are two main ways to explain something: say what "brought it about", or describe it at a more "fundamental" level. For ...
s, for example, that a certain building ''is'' in fact a bank and that certain paper ''is'' in fact money, which would seem to depend upon general recognition of those institutions and their value.


Indefinables

Indefinables are concepts so global that they cannot be defined; rather, in a sense, they themselves, and the objects to which they refer, define our reality and our ideas. Their meanings cannot be stated in a true definition, but their meanings can be referred to instead by being placed with their incomplete definitions in self-evident statements, the truth of which can be tested by whether or not it is impossible to think the opposite without a contradiction. Thus, the truth of indefinable concepts and propositions using them is entirely a matter of logic. An example of the above is that of the concepts "finite parts" and "wholes"; they cannot be defined without reference to each other and thus with some amount of circularity, but we can make the self-evident statement that "the whole is greater than any of its parts", and thus establish a meaning particular to the two concepts. These two notions being granted, it can be said that statements of "ought" are measured by their ''prescriptive'' truth, just as statements of "is" are measured by their ''descriptive'' truth; and the descriptive truth of an "is" judgment is defined by its correspondence to reality (actual or in the mind), while the prescriptive truth of an "ought" judgment is defined according to a more limited scope—its correspondence to right desire (conceivable in the mind and able to be found in the rational appetite, but not in the more "actual" reality of things independent of the mind or rational appetite).see To some, this may immediately suggest the question: "How can we know what is a right desire if it is already admitted that it is not based on the more actual reality of things independent of the mind?" The beginning of the answer is found when we consider that the concepts "good", "bad", "right" and "wrong" are indefinables. Thus, right desire cannot be defined properly, but a way to refer to its meaning ''may'' be found through a self-evident prescriptive truth.As an example of philosophical argumentation that identifies particular indefinables, we take "being" and then "good". Aristotle stated that although being is not a genus (''Posterior Analytics'' 2.7), yet of everything that is, being is predicated (''Topics'' 4.1), and that the Genus-differentia definitions, of which he was the first recorded proponent, requires that its subject be defined through its genus and a differentia. But since nothing lies outside of what is predicated of being, there is nothing which can serve as a differentia. So being is postulated to be indefinable. Later, Aquinas made an
argument An argument is a series of sentences, statements, or propositions some of which are called premises and one is the conclusion. The purpose of an argument is to give reasons for one's conclusion via justification, explanation, and/or persu ...
that stated, "Good and being are really the same, and differ only according to reason.... od presents the aspect of desirableness, which being does not present." (''Summa Theologica'', Part I, Q. 5, Art. 1) So good is postulated to be indefinable.
That self-evident truth which the moral cognitivist claims to exist upon which all other prescriptive truths are ultimately based is: ''One ought to desire what is really good for one and nothing else.'' The terms "real good" and "right desire" cannot be defined apart from each other, and thus their definitions would contain some degree of circularity, but the stated self-evident truth indicates a meaning particular to the ideas sought to be understood, and it is (the moral cognitivist might claim) impossible to think the opposite without a contradiction. Thus combined with other descriptive truths of what is good (goods in particular considered in terms of whether they suit a particular end and the limits to the possession of such particular goods being compatible with the general end of the possession of the total of all real goods throughout a whole life), a valid body of knowledge of right desire is generated.See for example


Functionalist counterexamples

Several counterexamples have been offered by philosophers claiming to show that there are cases when an "ought" logically follows from an "is." First of all,
Hilary Putnam Hilary Whitehall Putnam (; July 31, 1926 – March 13, 2016) was an American philosopher, mathematician, computer scientist, and figure in analytic philosophy in the second half of the 20th century. He contributed to the studies of philosophy of ...
, by tracing back the quarrel to Hume's dictum, claims fact/value entanglement as an objection, since the distinction between them entails a value. A. N. Prior points out, from the statement "He is a sea captain," it logically follows, "He ought to do what a sea captain ought to do."
Alasdair MacIntyre Alasdair Chalmers MacIntyre (12 January 1929 – 21 May 2025) was a Scottish-American philosopher who contributed to moral and political philosophy as well as history of philosophy and theology. MacIntyre's '' After Virtue'' (1981) is one of ...
points out, from the statement "This watch is grossly inaccurate and irregular in time-keeping and too heavy to carry about comfortably," the evaluative conclusion validly follows, "This is a bad watch." John Searle points out, from the statement "Jones promised to pay Smith five dollars," it logically follows that "Jones ought to pay Smith five dollars." The act of promising by definition places the promiser under obligation.


Moral realism

Philippa Foot adopts a moral realist position, criticizing the idea that when evaluation is superposed on fact there has been a "committal in a new dimension." She introduces, by analogy, the practical implications of using the word "injury." Not just anything counts as an injury. There must be some impairment. If one supposes a man wants the things the injury prevents him from obtaining, has one fallen into the old naturalist fallacy? She states the following: Foot argues that the virtues, like hands and eyes in the analogy, play so large a part in so many operations that it is implausible to suppose that a committal in a non-naturalist dimension is necessary to demonstrate their goodness.


Misunderstanding

Hilary Putnam Hilary Whitehall Putnam (; July 31, 1926 – March 13, 2016) was an American philosopher, mathematician, computer scientist, and figure in analytic philosophy in the second half of the 20th century. He contributed to the studies of philosophy of ...
argues that philosophers who accept Hume's "is–ought" distinction reject his reasons in making it, and thus undermine the entire claim. Various scholars have also indicated that, in the very work where Hume argues for the is–ought problem, Hume himself derives an "ought" from an "is". Such seeming inconsistencies in Hume have led to an ongoing debate over whether Hume actually held to the is–ought problem in the first place, or whether he meant that ought inferences can be made but only with good argumentation.


See also


References


Further reading

* * *


External links

*
Is Ought Problem animation from The Open University and BBC Radio 4
{{DEFAULTSORT:Is-ought problem 1739 introductions Concepts in ethics Concepts in metaphysics David Hume Dichotomies Humeanism Metaethics Philosophical problems