Q: What do we perceive directly? The Arguments from Illusion & Hallucination

Transcription

1 Recap: Lecture 7 Q: What do we perceive directly? (Or: What are epistemically basic empirical beliefs about?) The Arguments from Illusion & Hallucination In cases of illusion and hallucination, we do not directly perceive physical objects, but sense-data Cases of illusion and hallucination are of the same kind as other types of perceptual experience Therefore, we never directly perceive physical objects, but always directly perceive sense-data

2 8. The Sense-Datum Theory Physical Object causes Sense- Datum Sensation of sense-datum justifies Belief about physical object justifies Inductive Inference Epistemically basic belief about sense- Datum

3 Physical Object Causes Sense-Datum Physical (material) object: e.g. tomato, table Causes sense-datum to exist: reflects light, light strikes the eye, causes activity in brain Sense-datum: the given 1. Non-physical 2. Mind-dependent for sense-data, to exist is to be perceived (cf. Berkeley) 3. Appears exactly the way it is if it appears F, then it is F if it is F, then it appears F

4 Physical Object Causes Sense-Datum 1. Sense-data are non-physical According to physicalists (also called: naturalists, materialists), the physical world is causally closed Every physical event has complete physical cause If so: if sense-data exist, they are epiphenomenal They do not causally affect the physical world Reply: do sense-data need to have causal effects? Awareness of sense-datum is a non-causal relation. Q: Is this convincing? Why?

5 Physical Object Causes Sense-Datum 2. Sense-data are mind-dependent Suppose a non-philosophical observer gazing idly though a window. To him we address the request, Give us a description of your current visual experience, or How is it with you, visually, at the moment? Uncautioned as to exactly what we want, he might reply in some such terms as these: I see the red light of the setting sun filtering through the black and thickly clustered branches of the elms; I see the dappled deer grazing in groups on vivid green grass and so on. P.F. Strawson, Perception and its Objects, in G. McDonald ed. Perception and Identity (1979), reprinted in J. Dancy ed. Perceptual Knowledge (1988).

6 Physical Object Causes Sense-Datum 2. Sense-data are mind-dependent The transparency of experience Positive: we appear to be aware of mindindependent physical objects Negative: we do not appear to be aware of minddependent non-physical objects Reply: we can become aware of sense-data by focussing attention. Cf. the painter. Q: Is this convincing? Why?

7 Physical Object Causes Sense-Datum 3. Sense-data appear the way they are Each sample (supposedly!) looks the same as its neighbour Sameness is transitive : if A is the same as B, B is the same as C, then A is the same as C. (A law of identity.) But the first sample does not look the same as the last!

8 Physical Object Causes Sense-Datum 3. Sense-data appear the way they are Same as not a transitive relation: violates law of identity. Looks the same as not a transitive relation, i.e. A and B look the same, but are not really the same: but then sensedata can appear other than they really are.

9 Physical Object Causes Sense-Datum 3. Sense-data appear the way they are

10 Physical Object Causes Sense-Datum 3. Sense-data appear the way they are Do not perceive the hen to have a determinate number of speckles Sense-datum has indeterminate number of speckles: but a weird kind of object. Sense-datum has determinate number of speckles, but we are not aware of how many: but then sense-data do not appear the way they are. For both objections, see Armstrong, Perception and Belief, (pp ), Week 6

11 8. The Sense-Datum Theory Physical Object causes Sense- Datum Sensation of sense-datum justifies Belief about physical object justifies Inductive Inference Epistemically basic belief about sense- Datum

12 Sensation of sense-datum justifies epistemically basic belief Sensation of sense-datum Also: immediate apprehension of, direct awareness of Act-object: act = sensation, object = sense-datum Sensation distinct from sense-datum and belief about sense-datum. (Cf. Bonjour, p. 10 column 1.) Justifies the belief (e.g.) that there is something elliptical But how? Recall Bonjour s fundamental dilemma

13 Sensation of sense-datum justifies epistemically basic belief Either: Sensation is cognitive Represents sense-datum as being a certain way, e.g. ellipical Representations can be true (accurate) or false (inaccurate). Compare: beliefs, witness reports, paintings. If true, sensation of the sense-datum as elliptical justifies belief that the sense-datum is elliptical But if sensation could be false, then sensation itself requires justification: why suppose its not false now?

14 Sensation of sense-datum justifies epistemically basic belief Or: Sensation is non-cognitive Does not represent sense-datum as being a certain way, e.g. ellipical Only representations can be true or false If sensation can t be false, then it does not itself require justification But if sensation cannot be true, then sensation cannot justify the belief that the sense-datum is elliptical.

15 8. The Sense-Datum Theory Physical Object causes Sense- Datum Sensation of sense-datum justifies Belief about physical object justifies Inductive Inference Epistemically basic belief about sense- Datum

16 Belief about Physical Object Inferred from Belief about Sense-Datum Physical objects not (directly) seen. Existence and nature inductively inferred from beliefs about what is directly seen: sense-data. Inductive inference: some/many/all previous A s have been accompanied by B s, therefore some/many/all future A s will be accompanied by B s. E.g. smoke/fire, Hume s billiard balls Inference implicit or unconscious

17 Belief about Physical Object Inferred from Belief about Sense-Datum Veil of Perception Problem 1) Inference A B justified iff B has previously been seen to accompany A. 2) Inference sense-datum physical object justified iff physical object has previously been seen to accompany sense-datum 3) We never (directly) see physical objects 4) Therefore, inference sense-datum physical object not justified

18 Belief about Physical Object Inferred from Belief about Sense-Datum Permutation, e.g. inverted spectrum Physical Object Sense- Datum Belief

19 Belief about Physical Object Inferred from Belief about Sense-Datum Scientific Indirect Realism Physical Object a vast collection of electric charges in violent motion, Russell, p. 6 Sense- Datum Belief

20 Belief about Physical Object Inferred from Belief about Sense-Datum Something-We-Know-Not-What? Physical Object Sense- Datum Belief

21 Belief about Physical Object Inferred from Belief about Sense-Datum Idealism God Physical Object Sense- Datum Belief

22 Belief about Physical Object Inferred from Belief about Sense-Datum Nothing? Sense- Datum Belief Motivates phenomenalism : physical objects logical constructions of sense-data

23 8. The Sense-Datum Theory Physical Object causes Sense- Datum Sensation of sense-datum justifies Belief about physical object justifies Inductive Inference Epistemically basic belief about sensedatum

24 References D.M. Armstrong, Perception and Belief, from A Materialist Theory of Mind (London: Routledge, 1968). See Week 6. T. Crane, The Problem of Perception, Stanford Encylopedia of Philosophy. P.F. Strawson, Perception and its Objects, in G. McDonald ed. Perception and Identity (1979), reprinted in J. Dancy ed. Perceptual Knowledge (1988).