Deductive closure principle

2018 ◽  
Author(s):  
Anthony Brueckner
Keyword(s):  
External World ◽  
Sense Experience ◽  
Closure Principle ◽  
Logical Implication ◽  
Logic Of Knowledge ◽  
Body Of Knowledge ◽  
Sensory Evidence ◽  
Deductive Closure ◽  
Brain In A Vat ◽  
Sceptical Hypothesis

It seems that one can expand one’s body of knowledge by making deductive inferences from propositions one knows. The ‘deductive closure principle’ captures this idea: if S knows that P, and S correctly deduces Q from P, then S knows that Q. A closely related principle is that knowledge is closed under known logical implication: if S knows that P and S knows that P logically implies Q, then S knows that Q. These principles, if they hold, are guaranteed by general features of the concept of knowledge. They would form part of a logic of knowledge. An influential argument for scepticism about knowledge of the external world employs the deductive closure principle. The sceptic begins by sketching a logically possible hypothesis, or counter-possibility (for example, that one is a brain in a vat, with computer-induced sense experience) which is logically incompatible with various things one claims to know (such as that one has hands). The proposition that one has hands logically implies the falsity of the sceptical hypothesis. Supposing that one is aware of this implication, the deductive closure principle yields the consequence that if one knows that one has hands, then one knows that one is not a brain in a vat. The sceptic argues that one does not know this: if one were in a vat, then one would have just the sensory evidence one actually has. It follows that one does not know that one has hands. Some philosophers have sought to block this argument by denying the deductive closure principle.

Deductive closure principle

2018 ◽  
Author(s):  
Kelly Becker
Keyword(s):  
General Principle ◽  
External World ◽  
Theory Of Knowledge ◽  
Closure Principle ◽  
Rhetorical Device ◽  
Deductive Closure ◽  
Brain In A Vat ◽  
Philosophical Questions

The deductive closure principle is based on the thought that one straightforward way to extend one’s knowledge is to competently deduce some proposition from one or more propositions that one already knows. G.E. Moore (1939) appears to presume this in his proof of an external world. Updating Moore’s proof to incorporate the more recent rhetorical device of a brain-in-a-vat (BIV), from his putative knowledge that he has hands and his knowledge that his having hands entails that he is not merely a BIV being fed experiences, through electrodes, of having hands, Moore deduces and therefore claims to know that he is not a BIV. A natural sceptical reply also exploits the idea that one can extend one’s knowledge through deduction. The sceptic will say, for example, that Moore does not know that he is not a brain-in-a-vat (BIV), for if he were his experience would be no different to what it actually is. Moore does know, however, that if he has hands then he is not (just) a BIV. Therefore, Moore does not even know that he has hands, for if he did, he could deduce and come to know that he is not a BIV, but that is not something he can know because, again, his vat experiences would be indistinguishable from normal ones. The idea that knowledge can always be extended through competent deduction from known premises – which implies that knowledge is deductively closed under known entailment – raises at least three philosophical questions. First, what general principle best captures this phenomenon? Due primarily to risk arising from the fallibility of belief-forming processes including deduction, there is reason to question even the most plausible formulations of closure. Second, are there any counterexamples to the principle or constraints on its application? Some philosophers claim that a properly formulated closure principle admits of exceptions, even if deduction is assumed to be infallible. Third, how might a theory of knowledge that upholds a robust (exceptionless) closure principle achieve anti-sceptical results?.

Two Substantively Moorean Responses and the Project of Refuting Skepticism

2018 ◽  
Author(s):  
Keith DeRose
Keyword(s):  
External World ◽  
Semantic Externalism ◽  
Adequate Response ◽  
Brain In A Vat

In this chapter, substantive Mooreanism, according to which one does know that one is not a brain in a vat, is explained, and two main varieties of it are distinguished. Contextualist Mooreanism, (a) on which it is only claimed that one knows that one is not a brain in a vat according to ordinary standards for knowledge, and (b) on which one seeks to defeat bold skepticism (according to which one doesn’t know simple, seemingly obvious truths about the external world, even by ordinary standards for knowledge), is contrasted with Putnam-style responses, on which one seeks to refute the skeptic, utilizing semantic externalism. Problems with the Putnam-style attempt to refute skepticism are identified, and then, more radically, it is argued that in important ways, such a refutation of skepticism would not have provided an adequate response to skepticism even if it could have been accomplished.

Epistemic and Doxastic Contents

2019 ◽  
pp. 213-238
Author(s):  
Francesco Berto ◽  
Mark Jago
Keyword(s):  
Bounded Rationality ◽  
Logical Consequence ◽  
External World ◽  
Belief State ◽  
Impossible Worlds ◽  
Formal Models ◽  
Closure Principle ◽  
Primary Focus ◽  
Belief States ◽  
Trivial Consequence

The case for making belief states the primary focus of our analysis and for including impossible worlds in that analysis is outlined in this chapter. This allows the reader to deny various closure principles, although this won’t help defeat worries about external-world scepticism. The issue that concerns the authors most is the problem of bounded rationality: belief states seem to be closed under ‘easy’ trivial consequence, but not under full logical consequence, and yet the former implies the latter. The solution presented here is that some trivial closure principle must fail on a given belief state, yet it is indeterminate just where this occurs. Formal models of belief states along these lines are given and it is shown that they respect the indeterminacy-of-closure intuition. Finally, the chapter discusses how we might square this approach with the fact that some people seem to believe contradictions.

Linguistic Philosophy and Perception

Philosophy ◽  
1953 ◽  
Vol 28 (107) ◽  
pp. 311-324
Author(s):  
Margaret MacDonald
Keyword(s):  
Moral Philosophy ◽  
Common Sense ◽  
External World ◽  
Physical World ◽  
Sense Experience ◽  
The Common ◽  
The Senses ◽  
Perceptual Variation ◽  
Linguistic Philosophy ◽  
As If

Philosophical theories of perception are generally admitted to be responses to certain problems or puzzles allied to the ancient dichotomy between Appearance and Reality. For they have been mainly provoked by the incompatibility of the common–sense assumption that an external, physical world exists and is revealed to the senses with the well–known facts of perceptual variation and error. If only what is real were perceived just as if only what is right were done it is possible that many of those questions would never have been asked which lead to moral philosophy and a metaphysics of the external world. But sense perceptions of the same object vary so that it appears to have contradictory qualities and are sometimes completely deceptive. Nor do illusory differ internally from veridical perceptions. Moreover, perceptual variation and error can be unmasked only by such procedures as looking more carefully, listening harder, trying to touch, asking others, in short by more sense experience. So the senses are, as it were, both accused and judge in these disputes and why should a venal judge be trusted more than the criminal he tries? Such “correction” of one experience by another of the same kind seems no more reliable than the original “error.” Philosophers have found all this very puzzling.

scholarly journals http://habibiaislamicus.com/index.php/hirj/article/view/150

2021 ◽  
Vol 5 (3) ◽  
pp. 121-138
Author(s):  
Wajid Ali ◽  
Keyword(s):  
The Other ◽  
Human Being ◽  
Human Beings ◽  
Sense Experience ◽  
Intuitive Thinking ◽  
Body Of Knowledge ◽  
Depth Study ◽  
The Universe

Allah (swt) has elevated man to the highest position in all creation, and bestwed upon him the bounty of reason and knowledge. An in depth study of knowledge itself reveals that, there are two forms and ranks of knowledge in the universe; one is the divinely revealed instintintive level of awareness about reality, and the other is the earned and learned behavoiur based upon knowledge, that is gained through urge, effort and experience. Human beings, apart from the innate divine blessing of knowledge, learns through sense experience, reason and intuitive thinking. The higher form of knowledge is divinely transmission through revelation to the Prophets. The heavenly revealed knowledge has been preserved by human being in the form of Sacred Books; especially a body of knowledge about reality in the form of religion, namely in the Holy Bible and the Holy Qur’an.

scholarly journals Skepticism and Epistemic Closure: Two Bayesian Accounts

2017 ◽  
Vol 7 (1) ◽  
pp. 1-25 ◽  
Author(s):  
Luca Moretti ◽  
Tomoji Shogenji
Keyword(s):  
External World ◽  
The Body ◽  
Component Model ◽  
Epistemic Closure ◽  
Sense Experience ◽  
Evil Demon ◽  
The Third ◽  
First Response ◽  
Skeptical Paradox

This paper considers two novel Bayesian responses to a well-known skeptical paradox. The paradox consists of three intuitions: first, given appropriate sense experience, we have justification for accepting the relevant proposition about the external world; second, we have justification for expanding the body of accepted propositions through known entailment; third, we do not have justification for accepting that we are not disembodied souls in an immaterial world deceived by an evil demon. The first response we consider rejects the third intuition and proposes an explanation of why we have a faulty intuition. The second response, which we favor, accommodates all three intuitions; it reconciles the first and the third intuition by the dual component model of justification, and defends the second intuition by distinguishing two principles of epistemic closure.

2. Is knowledge impossible?

2019 ◽  
pp. 23-46
Author(s):  
Duncan Pritchard
Keyword(s):  
Epistemic Reasons ◽  
Closure Principle ◽  
Theoretical Innovation ◽  
Radical Scepticism ◽  
Sceptical Paradox ◽  
Sceptical Hypothesis ◽  
Sceptical Argument

‘Is knowledge impossible?’ considers an influential argument that purports to show that we do not know much of what we take ourselves to know. If this argument works, then it licenses a radical sceptical doubt. It first looks at Descartes’s formulation of radical scepticism—Cartesian scepticism—which employs an important theoretical innovation known as a radical sceptical hypothesis. The closure principle is also discussed along with the radical sceptical paradox. If this radical sceptical argument works, then we not only lack knowledge of much of what we believe, but we do not even have any good epistemic reasons for believing what we do.

A Sellarsian Transcendental Argument against External World Skepticism

2020 ◽  
pp. 1-31
Author(s):  
Marin Geier
Keyword(s):  
External World ◽  
Transcendental Argument ◽  
Wilfrid Sellars ◽  
Rule Following ◽  
External World Skepticism ◽  
The Brain ◽  
Brain In A Vat

This paper investigates the relation between what James Conant has called Kantian and Cartesian varieties of skepticism. It is argued that a solution to the most prominent example of a Kantian variety of skepticism, i.e. Kripkensteinian skepticism about rule-following and meaning, can be found in the works of Wilfrid Sellars. It is then argued that, on the basis of that very same solution to the Kantian problematic of rule-following and meaning, a novel argument against external world skepticism can be formulated. This argument takes the shape of a transcendental argument, which is reminiscent of Hilary Putnam’s infamous argument against the brain-in-a-vat hypothesis, but is, as is argued, superior to it in certain respects.

A Problem for the Closure Argument

2014 ◽  
Vol 4 (1) ◽  
pp. 36-49 ◽  
Author(s):  
Philip Atkins ◽  
Ian Nance
Keyword(s):  
External World ◽  
Correct Classification ◽  
Closure Principle ◽  
Begging The Question ◽  
Transmission Failure ◽  
The Subject

Contemporary discussions of skepticism often frame the skeptic’s argument around an instance of the closure principle. Roughly, the closure principle states that if a subject knows p, and knows that p entails q, then the subject knows q. The main contention of this paper is that the closure argument for skepticism is defective. We explore several possible classifications of the defect. The closure argument might plausibly be classified as begging the question, as exhibiting transmission failure, or as structurally inefficient. Interestingly, perhaps, each of these has been proposed as the correct classification of Moore’s proof of an external world.

Pluralist Consequentialist Anti-Scepticism

2020 ◽  
pp. 297-326
Author(s):  
Nikolaj J. L. L. Pedersen
Keyword(s):  
External World ◽  
Epistemic Rationality ◽  
Epistemic Value ◽  
Crispin Wright ◽  
Absence Of Evidence ◽  
Brain In A Vat

How could it be warranted and rational to accept anti-sceptical hypotheses (I’m not a brain in a vat, There is an external world, etc.) in the absence of evidence supporting such propositions? Crispin Wright has introduced entitlement of cognitive project—a non-evidential species of warrant—as a response to the sceptic. Critics (Pritchard and Jenkins) have argued that Wright-style entitlement is not an epistemic kind of warrant and does not sustain epistemic rationality. This chapter develops a consequentialist alternative to Wright’s proposal. Acceptance of anti-sceptical hypotheses is epistemically warranted and rational because it maximizes epistemic value. This is argued within an axiological framework that incorporates pluralism about epistemic value or goods. Truth is not the only epistemic good—contra veritic monism, the most widely held view about epistemic value. Furthermore, the chapter argues that the success of the consequentialist approach eliminates the need for Wright-style entitlement.

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