Epistemic closure
is a
property
Property is a system of rights that gives people legal control of valuable things, and also refers to the valuable things themselves. Depending on the nature of the property, an owner of property may have the right to consume, alter, share, r ...
of some
belief system
A belief is an attitude that something is the case, or that some proposition is true. In epistemology, philosophers use the term "belief" to refer to attitudes about the world which can be either true or false. To believe something is to take ...
s. It is the
principle that if a subject
knows
, and
knows that
entails , then
can thereby come to know
. Most
epistemological theories
A theory is a rational type of abstract thinking about a phenomenon, or the results of such thinking. The process of contemplative and rational thinking is often associated with such processes as observational study or research. Theories may be ...
involve a closure principle and many
skeptical
Skepticism, also spelled scepticism, is a questioning attitude or doubt toward knowledge claims that are seen as mere belief or dogma. For example, if a person is skeptical about claims made by their government about an ongoing war then the p ...
arguments assume a closure principle.
On the other hand, some epistemologists, including
Robert Nozick, have denied closure principles on the basis of
reliabilist accounts of knowledge. Nozick, in ''
Philosophical Explanations
''Philosophical Explanations'' is a 1981 metaphysical, epistemological, and ethical treatise by the philosopher Robert Nozick.
The book received positive reviews. Commentators have compared ''Philosophical Explanations'' to the philosopher Richa ...
'', advocated that, when considering the
Gettier problem
The Gettier problem, in the field of epistemology, is a landmark philosophical problem concerning the understanding of descriptive knowledge. Attributed to American philosopher Edmund Gettier, Gettier-type counterexamples (called "Gettier-cases") ...
, the least counter-intuitive assumption we give up should be epistemic closure. Nozick suggested a "truth tracking" theory of knowledge, in which the x was said to know P if x's belief in P tracked the truth of P through the relevant
modal scenarios.
A subject may not actually believe
q, for example, regardless of whether he or she is justified or warranted. Thus, one might instead say that knowledge is closed under ''known'' deduction: if, while knowing
p,
S believes
q because
S knows that
p entails
q, then
S knows
q.
An even stronger formulation would be as such: If, while knowing various propositions,
S believes
p because
S knows that these propositions entail
p, then
S knows
p.
While the principle of epistemic closure is generally regarded as intuitive, philosophers such as Robert Nozick and
Fred Dretske
Frederick Irwin "Fred" Dretske (; December 9, 1932 – July 24, 2013) was an American philosopher noted for his contributions to epistemology and the philosophy of mind.
Biography
Born to Frederick and Hattie Dretske, Dretske first planned to be ...
have argued against it.
Epistemic closure and skeptical arguments
The epistemic closure principle typically takes the form of a
modus ponens argument:
# S knows p.
# S knows that p entails q.
# Therefore, S knows q.
This epistemic closure principle is central to many versions of skeptical arguments. A
skeptical
Skepticism, also spelled scepticism, is a questioning attitude or doubt toward knowledge claims that are seen as mere belief or dogma. For example, if a person is skeptical about claims made by their government about an ongoing war then the p ...
argument of this type will involve knowledge of some piece of widely accepted information to be knowledge, which will then be pointed out to entail knowledge of some skeptical scenario, such as the
brain in a vat
In philosophy, the brain in a vat (BIV) is a scenario used in a variety of thought experiments intended to draw out certain features of human conceptions of knowledge, reality, truth, mind, consciousness, and meaning. It is a modern incarna ...
scenario or the
Cartesian evil demon scenario. A skeptic might say, for example, that if you know that you have hands, then you know that you are not a handless brain in a vat (because knowledge that you have hands implies that you know you are not handless, and if you know that you are not handless, then you know that you are not a handless brain in a vat). The skeptic will then utilize this conditional to form a
modus tollens
In propositional logic, ''modus tollens'' () (MT), also known as ''modus tollendo tollens'' (Latin for "method of removing by taking away") and denying the consequent, is a deductive argument form and a rule of inference. ''Modus tollens' ...
argument. For example, the skeptic might make an argument like the following:
# You do not know that you are not a handless brain in a vat (~K(~h))
# If you know that you have hands, then you know that you are not a handless brain in a vat (K(o) → K(~h))
# Conclusion: Therefore, you do not know that you have hands (~K(o))
Much of the epistemological discussion surrounding this type of skeptical argument involves whether to accept or deny the conclusion, and how to do each.
Ernest Sosa
Ernest Sosa (born June 17, 1940) is an American philosopher primarily interested in epistemology. Since 2007 he has been Board of Governors Professor of Philosophy at Rutgers University, but he spent most of his career at Brown University.
Educa ...
says that there are three possibilities in responding to the skeptic:
# Agree with the skeptic by granting him both premises and the conclusion (1, 2, c)
# Disagree with the skeptic by denying premise 2 and the conclusion, but maintaining premise 1 (1, ~2, ~c) as
Nozick and
Dretske do. This amounts to ''denying'' the epistemic closure principle.
# Disagree with the skeptic by denying premise 1 and the conclusion, but maintaining premise 2 (~1, 2, ~c) as
Moore does. This amounts to ''maintaining'' the epistemic closure principle, and holding that knowledge is closed under known
implication.
Justificatory closure
In the seminal 1963 paper, “
Is Justified True Belief Knowledge?”, Edmund Gettier gave an assumption (later called the “principle of deducibility for justification” by
Irving Thalberg, Jr.
Irving Grant Thalberg Jr. (August 25, 1930August 21, 1987) was an author and the son of 1930s Hollywood producer Irving Thalberg and Academy Award-winning actress Norma Shearer.
Thalberg was six years old when his father died from pneumonia at ...
) that would serve as a basis for the rest of his piece: “for any proposition P, if S is justified in believing P and P entails Q, and S deduces Q from P and accepts Q as a result of this deduction, then S is justified in believing Q.” This was seized upon by Thalberg, who rejected the principle in order to demonstrate that one of Gettier's examples fails to support Gettier's main thesis that justified true belief is not knowledge (in the following quotation, (1) refers to “Jones will get the job”, (2) refers to “Jones has ten coins”, and (3) is the
logical conjunction
In logic, mathematics and linguistics, And (\wedge) is the truth-functional operator of logical conjunction; the ''and'' of a set of operands is true if and only if ''all'' of its operands are true. The logical connective that represents thi ...
of (1) and (2)):
Why doesn't Gettier's principle (PDJ) hold in the evidential situation he has described? You multiply your risks of being wrong when you believe a conjunction. Te most elementary theory of probability indicates that Smith's prospects of being right on both (1) and (2), namely, of being right on (3), are bound to be less favorable than his prospects of being right on either (1) or (2). In fact, Smith's chances of being right on (3) might not come up to the minimum standard of justification which (1) and (2) barely satisfy, and Smith would be unjustified in accepting (3).
Epistemic closure in U.S. political discussion
The term "epistemic closure" has been used in an unrelated sense in American political debate to refer to the claim that political belief systems can be closed systems of deduction, unaffected by
empirical evidence
Empirical evidence for a proposition is evidence, i.e. what supports or counters this proposition, that is constituted by or accessible to sense experience or experimental procedure. Empirical evidence is of central importance to the sciences ...
.
This use of the term was popularized by libertarian blogger and commentator
Julian Sanchez in 2010 as an extreme form of
confirmation bias.
References
External links
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{{epistemology
Concepts in epistemology
Belief
Modal logic
Philosophy of Robert Nozick