牛津大学开放课程哲学概论ppt讲解三.pdf

General PhilosophyGeneral Philosophy Dr Peter Millican, Hertford CollegeDr Peter Millican, Hertford College Lecture 3:Lecture 3: InductionInduction 2 2 HumeHume’ ’s Forks Fork EnquiryEnquiry IV starts with a vital distinction IV starts with a vital distinction between types of proposition:between types of proposition: – – Relations of ideasRelations of ideas can be known can be known a prioria priori (i.e. (i.e. without dependence on experience) bywithout dependence on experience) by inspecting ideas; hence their falsehood isinspecting ideas; hence their falsehood is inconceivable and they are necessarily true.inconceivable and they are necessarily true. e.g.e.g.PythagorasPythagoras’ ’ Theorem. ( Theorem. (E E 4.1) 4.1) 3 3 × 5 = ½ × 30. (× 5 = ½ × 30. (E E 4.1) 4.1) All bachelors are unmarried.All bachelors are unmarried. – – The modern term is The modern term is analyticanalytic (as understood (as understood e.g. by Ayer): e.g. by Ayer): “ “true in virtue of its meaningtrue in virtue of its meaning” ”. . 3 3 Matters of FactMatters of Fact – – Matters of factMatters of fact can can’ ’t be known t be known a prioria priori, and their, and their truth / falsity are equally conceivable:truth / falsity are equally conceivable: e.g.e.g.The sun will rise tomorrow. (The sun will rise tomorrow. (E E 4.2) 4.2) The sun will not rise tomorrow. The sun will not rise tomorrow. ( (E E 4.2) 4.2) This pen will fall when released in air.This pen will fall when released in air. – – The modern term is The modern term is syntheticsynthetic: a proposition: a proposition whose truth whose truth “ “is determined by the facts ofis determined by the facts of experienceexperience” ” (Ayer, (Ayer, LTLLTL 1971, p. 105). 1971, p. 105). So how can I discover a matter of fact whichSo how can I discover a matter of fact which I neither perceive directly, nor remember?I neither perceive directly, nor remember? 4 4 Suppose we see a yellow billiard ball movingSuppose we see a yellow billiard ball moving towards a red one and colliding with it. Wetowards a red one and colliding with it. We expect the red one to move expect the red one to move – – but why? but why? Because we suppose a Because we suppose a causal causal connexionconnexion between the two events. But in that case between the two events. But in that case …… How do we learn about causes and effects?How do we learn about causes and effects? 5 5 A Thought ExperimentA Thought Experiment Imagine Adam, newly created by God,Imagine Adam, newly created by God, trying to envisage the effect of the collision:trying to envisage the effect of the collision: – – how could he possibly how could he possibly make any prediction at allmake any prediction at all in advance of experience?in advance of experience? 6 6 The Need for ExtrapolationThe Need for Extrapolation All inference to matters of fact beyond whatAll inference to matters of fact beyond what we perceive or remember seems to be basedwe perceive or remember seems to be based on causation, and all our knowledge ofon causation, and all our knowledge of causal relations comes from experience.causal relations comes from experience. Such learning from experience takes forSuch learning from experience takes for granted that observed phenomena provide agranted that observed phenomena provide a guide to unobserved phenomena.guide to unobserved phenomena. We thus We thus extrapolateextrapolate from past to future on from past to future on the assumption that they resemble. But dothe assumption that they resemble. But do we have a rational basis for doing so?we have a rational basis for doing so? 7 7 Four Four “ “Kinds of EvidenceKinds of Evidence” ” “ “It is common for Philosophers to distinguish theIt is common for Philosophers to distinguish the Kinds of Evidence into Kinds of Evidence into intuitiveintuitive, , demonstrativedemonstrative, , sensiblesensible, , and moraland moral” ”. (. (Letter from a GentlemanLetter from a Gentleman, , 1745, p. 22)1745, p. 22) By By “ “intuitionintuition” ”, Hume means immediate self-, Hume means immediate self- evidence: the way we know that something isevidence: the way we know that something is identical with itself, or that 2 is greater than 1.identical with itself, or that 2 is greater than 1. “ “SensibleSensible” ” evidence means evidence means from the sensesfrom the senses. . “ “DemonstrativeDemonstrative” ” and and “ “moralmoral” ” reasoning are now reasoning are now commonly called commonly called “ “deductiondeduction” ” and and “ “inductioninduction” ” …… 8 8 Locke on ReasoningLocke on Reasoning In In demonstrativedemonstrative reasoning, each link in the reasoning, each link in the inferential chain is inferential chain is “ “intuitivelyintuitively” ” certain. certain. – – “ “reasoning concerning relations of ideasreasoning concerning relations of ideas” ” [Hume] [Hume] In In probable reasoningprobable reasoning, some links in the, some links in the inferential chain are merely probable.infer。