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Single Idea 6372

[filed under theme 14. Science / C. Induction / 6. Bayes's Theorem ]

Full Idea

It follows from the probability calculus that every tautology has probability 1; it then follows in Bayesian epistemology that we are justified in believing every tautology.

Gist of Idea

Since every tautology has a probability of 1, should we believe all tautologies?

Source

J Pollock / J Cruz (Contemporary theories of Knowledge (2nd) [1999], §4.3.1.5)

Book Ref

Pollock,J.L./Cruz,J: 'Contemporary Theories of Knowledge (2nd)' [Rowman and Littlefield 1999], p.105

A Reaction

If I say 'a bachelor is a small ant' you wouldn't believe it, but if I said 'I define a bachelor as a small ant' you would have to believe it. 'Bachelors are unmarried' men is a description of English usage, so is not really a simple tautology.

The 22 ideas from J Pollock / J Cruz

6346 The main epistemological theories are foundationalist, coherence, probabilistic and reliabilist [Pollock/Cruz]
6351 Most people now agree that our reasoning proceeds defeasibly, rather than deductively [Pollock/Cruz]
6352 Enumerative induction gives a universal judgement, while statistical induction gives a proportion [Pollock/Cruz]
6354 Coherence theories fail, because they can't accommodate perception as the basis of knowledge [Pollock/Cruz]
6355 Direct realism says justification is partly a function of pure perceptual states, not of beliefs [Pollock/Cruz]
6353 People rarely have any basic beliefs, and never enough for good foundations [Pollock/Cruz]
6357 Reason cannot be an ultimate foundation, because rational justification requires prior beliefs [Pollock/Cruz]
6358 One belief may cause another, without being the basis for the second belief [Pollock/Cruz]
6359 Phenomenalism offered conclusive perceptual knowledge, but conclusive reasons no longer seem essential [Pollock/Cruz]
6360 Scientific confirmation is best viewed as inference to the best explanation [Pollock/Cruz]
6361 Foundationalism requires self-justification, not incorrigibility [Pollock/Cruz]
6362 Sense evidence is not beliefs, because they are about objective properties, not about appearances [Pollock/Cruz]
6363 Foundationalism is wrong, because either all beliefs are prima facie justified, or none are [Pollock/Cruz]
6364 We can't start our beliefs from scratch, because we wouldn't know where to start [Pollock/Cruz]
6365 Negative coherence theories do not require reasons, so have no regress problem [Pollock/Cruz]
6366 Perception causes beliefs in us, without inference or justification [Pollock/Cruz]
6367 Coherence theories isolate justification from the world [Pollock/Cruz]
6370 Externalism comes as 'probabilism' (probability of truth) and 'reliabilism' (probability of good cognitive process) [Pollock/Cruz]
6371 Bayesian epistemology is Bayes' Theorem plus the 'simple rule' (believe P if it is probable) [Pollock/Cruz]
6372 Since every tautology has a probability of 1, should we believe all tautologies? [Pollock/Cruz]
6373 Internalism says if anything external varies, the justifiability of the belief does not vary [Pollock/Cruz]
6374 To believe maximum truths, believe everything; to have infallible beliefs, believe nothing [Pollock/Cruz]