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?.

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.

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.

Whose Dream Is It Anyway?

2014 ◽  
Vol 4 (3-4) ◽  
pp. 263-287
Author(s):  
Avner Baz
Keyword(s):  
Ordinary Language ◽  
External World ◽  
Theory Of Knowledge ◽  
Second Line ◽  
Ordinary Language Philosophy ◽  
First Line ◽  
Standard Type ◽  
Language Philosophy ◽  
Cartesian Skepticism

I start with two basic lines of response to Cartesian skepticism about the ‘external world’: in the first, which is characteristic of Analytic philosophers to this day, the focus is on the meaning of ‘know’—what it ‘refers’ to, its ‘semantics’ and its ‘pragmatics’; in the second, which characterizes Continental responses to Descartes, the focus is on the philosophizing or meditating subject, and its relation to its body and world. I argue that the first approach is hopeless: if the Cartesian worry that I could be dreaming right now so much as makes sense, the proposal that—under some theory of knowledge (or of ‘knowledge’)—my belief that I am sitting in front of the computer right now may still be (or truly count as) a piece of knowledge, would rightfully seem to the skeptic to be playing with words and missing the point. I then argue that the practice of Ordinary Language Philosophy, which has mostly been linked to the first line of response to Cartesian skepticism, may be seen as actually belonging with the second line of response; and I show how a form of what may be called “Existentialist Ordinary Language Philosophy” can be used to reveal the nonsensicality of the Cartesian skeptical worry. My argument takes its cue from Thompson Clarke’s insight—an insight that Clarke himself has not pursued far or accurately enough—that our concept of Dream is not a concept of the “standard type.”

scholarly journals Charles Peirce's Theory of Scientific Method

1970 ◽  
Author(s):  
Francis E. Reilly
Keyword(s):  
Scientific Inquiry ◽  
Scientific Method ◽  
Significant Part ◽  
Theory Of Knowledge ◽  
Theoretical Knowledge ◽  
Rich Diversity ◽  
Complex Thought ◽  
Double Approach ◽  
The Rich ◽  
Philosophical Questions

This book is an attempt to understand a significant part of the complex thought of CharlesSanders Peirce, especially in those areas which interested him most: scientific method and related philosophical questions. It is organized primarily from Peirce's own writings, taking chronological settings into account where appropriate, and pointing out the close connections of several major themes in Peirce's work which show the rich diversity of his thought and its systematic unity. Following an introductory sketch of Peirce the thinking and writer is a study of the spirit and phases of scientific inquiry, and a consideration of its relevance to certain outstanding philosophical views which Peirce held. This double approach is necessary because his views on scientific method are interlaced with a profound and elaborate philosophy of the cosmos. Peirce's thought is unusually close-knit, and his difficulty as a writer lies in his inability to achieve a partial focus without bringing into view numerous connections and relations with the whole picture of reality. This book attempts to understand Peirce as Peirce intended himself to be understood, and has presented what the author believes Peirce's philosophy of scientific method to be. The book singles out for praise Peirce's Greek insistence on the primacy of theoretical knowledge and his almost Teilhardian synthesis of evolutionary themes. Primarily philosophical, this volume analyzes Peirce's thought using a theory of knowledge and metaphysics rather than formal logic.

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.

Exemplars of Truth

2018 ◽  
Author(s):  
Keith Lehrer
Keyword(s):  
External World ◽  
Theory Of Knowledge ◽  
Coherence Theory ◽  
Special Role ◽  
The Core ◽  
Intellectual System ◽  
The World ◽  
Key Topics ◽  
Modern Work

This monograph is both an intellectual summation as well as a philosophical advancement of key themes of the work of Keith Lehrer on several key topics—including knowledge, self-trust, autonomy, and consciousness. He here attempts to integrate these themes and develop an intellectual system that can constructively solve philosophical problems. The system is indebted to the modern work of Sellars, Quine, and Chisholm, as well as historically to Hume and Reid. At the core of this system lies Lehrer’s theory of knowledge, which he previously called a coherence theory of knowledge but now calls a defensibility theory. Lehrer argues that knowledge requires the capacity to justify or defend the target claim of knowledge in terms of a background system. Defensibility is an internal capacity supplied by that system to meet objections to the claim. This theory however leaves open the problem of “experience,” noted by other philosophers, of how to explain the special role of experience in a background system even granted we are fallible in describing it. Lehrer offers a solution to the problem of experience, arguing that reflection on experience converts the experience itself into an exemplar, something like a sample that becomes a vehicle or term of representation. The exemplar represents itself and extends to represent the external world. It exhibits something about evidence and truth concerning experience that, as Wittgenstein noted, cannot be fully described but can only be shown. Exemplar representation is the missing link of a background system to truth about the world.

Locke's "internal" questions

2004 ◽  
Vol 47 (1-2) ◽  
pp. 25-33
Author(s):  
Masan Bogdanovski
Keyword(s):  
External World ◽  
The Real ◽  
External Objects ◽  
Philosophical Questions ◽  
Internal Question

As Moore does in his proof of the external world, Locke asks the question about the existence of things external to our minds as, in Carnap's sense, an "internal" question. The real reason to be dissatisfied with Locke's causal arguments against skepticism is not that they fail to remove the skeptical alternatives imperiling our knowledge, but in the fact that they sidestep the philosophical skepticism, the characteristically "external" way of posing the philosophical questions about the knowledge of external objects.

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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