Realism and its competitors. Scepticism, idealism, phenomenalism

Transcription

1 Realism and its competitors Scepticism, idealism, phenomenalism

2 Perceptual Subjectivism Bonjour gives the term perceptual subjectivism to the conclusion of the argument from illusion. Perceptual subjectivism is the disjunction of two different views: the sense-datum theory and the adverbial theory. (And maybe direct realism too, as Huemer understands it.)

3 Perceptual subjectivism and scepticism Does perceptual subjectivism lead to scepticism? Hume seems to think so.

4 Hume on RR The table that we see seems to shrink as we move away from it; but the real table that exists independently of us doesn t alter; so what was present to the mind wasn t the real table but only an image of it. These are the obvious dictates of reason; and no-one who thinks about it has ever doubted that when we say this house and that tree the things we are referring to are nothing but perceptions in the mind fleeting copies or representations of other things that are independent of us and don t change.

5 But when philosophy tries to justify this new system, and put to rest the carping objections of the sceptics, it finds itself in an awkward position regarding the claim [representative realism] that there are external objects that our images represent. 1. Philosophy can no longer rely on the idea that natural instincts are infallible and irresistible, for those instincts led us to a quite different system that is admitted to be fallible and even wrong. 2. And to justify the external-object part of this purported philosophical system by a chain of clear and convincing argument or even by any appearance of argument is more than anyone can do.

6 N.B. Points 1 and 2 roughly respond to what (1) externalists and (2) internalists want to say in reponse to Hume s sceptical challenge. Is Hume right that our natural instincts cannot be trusted? E.g. Do tables appear to shrink as we move away from them? An we trust our natural instincts only if they re infallible?

7 Internalism vs. externalism Internalists say that knowledge requires justification from an internal, 1 st person perspective. I must be consciously aware of evidence that proves my belief. Externalists say that knowledge requires justification (or warrant ) from an external, 3 rd person perspective. I don t have to be aware of evidence supporting my belief. Warrant depends only on a good and proper connection between my belief and reality that exists in fact, i.e. from a 3 rd person perspective.

8 Hume s scepticism (point 2) By what argument can it be proved that the perceptions of the mind must be caused by external objects that are perfectly distinct from them and yet similar to them (if that were possible), rather than arising from the energy of the mind itself, or from the activities of some invisible and unknown spirit, or from some other cause still more unknown to us?... Where shall we look for an answer to it? To experience, surely, as we do with all other questions of that kind. But here experience is and must be entirely silent. The mind never has anything present to it except the perceptions, and can t possibly experience their connection with objects. The belief in such a connection, therefore, has no foundation in reasoning because the reasoning would have to start from something known through experience. (p. 2)

9 In order to learn from experience about what causes what, you have to experience both ends of the causal relation. E.g. in order to learn from experience that fire causes smoke, you have to experience fire-smoke firesmoke fire-smoke, etc. repeatedly. If you just experience smoke smoke smoke, then you can t know what the cause of the smoke is.

10 Regress of justification problem 1. In order to know something, I must have a good reason for believing it. 2. Any chain of reasons must have one of the following structures: Either (a) it is an infinite series, (b) it is circular, or (c) it begins with a belief for which there are no further reasons. But, 3. I cannot have an infinitely long chain of reasoning for any of my beliefs. 4. Circular reasoning cannot produce knowledge. 5. Nor can I gain knowledge by structure 2c. 6. Therefore, I cannot know anything.

11 Problem of the criterion Imagine there were a community in which use of the Magic Eight Ball was an accepted method of arriving at conclusions. Suppose you meet one of these eight-ball reasoners, and you ask him why he believes that the eight ball is a reliable informant. He swiftly takes out his Magic Eight Ball, says, Are you reliable? and turns it over. Suppose a definite Yes answer appears, and the eight-ball reasoner triumphantly declares that the reliability of the eight ball has been established. Would this be legitimate? (Michael Huemer, p. 11)

12 Now consider an analogous case. Suppose some skeptic comes along and asks you why you believe the senses to be reliable. Why do you think that, when you seem to see, hear, or feel things, this is a reliable indicator of the way things really are, in the external world? How would you respond? Is there anything you could say that would avoid the same vicious circularity that the eight-ball reasoner committed?

13 Representative Realism Realism: There is an external world that causes our sensations, and ultimately our beliefs about the external world. Under normal conditions, our beliefs are approximately true. We can have (approximate and fallible) knowledge of the external world. Representative: The objects in our conscious awareness (e.g. in the visual field) are internal representations, not external objects.

14 Locke s arguments for realism 1. Those lacking some sense organs also lack the corresponding ideas 2. Sensory ideas are involuntary 3. Some sensory ideas (but not imagined ideas) are accompanied by pain. 4. Sensory ideas are orderly and consistent. BonJour (and probably Locke) thinks that the these facts are best explained by the view that there is a stable external world causing the sensations. Alternative explanations?

15 Berkeley: objects as God s ideas Berkeley s idealism is a lot like the Cartesian demon scenario, except that it doesn t involve any deception according to Berkeley. There are no material substances, i.e. objects that exist, and have properties, independently of anyone perceiving them, and yet are able to cause us to form accurate ideas of them. Ordinary objects, such as chairs and tables, are actually ideas in the mind of God that are transmitted somehow to our minds. The world consists only of minds (divine and human) and their ideas.

16 Berkeley argues that his idealism is in accordance with common sense, even more than Locke s representational realism.) For example, Berkeley thinks that tomatoes really are red.

17 In order for the external world to be suitably solid and objective, e.g. for objects to continue to exist even when no human is perceiving them, a superperceiver (God) is required. The need for God is an advantage of the theory, for (Bishop) Berkeley.

18 God in the Quad by Ronald Knox There was a young man who said, "God Must think it exceedingly odd If he finds that this tree Continues to be When there's no one about in the Quad." REPLY Dear Sir: Your astonishment's odd: I am always about in the Quad. And that's why the tree Will continue to be, Since observed by Yours faithfully, GOD.

19 Berkeley s argument 1. sensible things = things that are perceived immediately by the senses. So sensible things are ideas. (Note that Berkeley Philonous-- believes that the senses make no inferences.)

20 2. Sensible objects are combinations of sensible qualities. (Bundle theory of internal objects.) E.g. a snowball-idea is the combination of whiteness, coldness, roundness, firmness, etc.

21 3. The reality of sensible things consists in being perceived. The notion of a pain, for example, that isn t felt by anyone, is silly. For sensible objects, esse est percipi (to be is to be perceived.

22 4. Then Hylas ( matter ) objects, saying that real objects must exist independently, without any need to be perceived. Philonous responds with Lockean arguments that some qualities cannot exist outside the mind. Heat, for example, is continuous with pain, and pain is only in minds. the intense heat immediately perceived is nothing distinct from a certain sort of pain.

23 5. Hylas yields, agreeing that heat and cold are not in the objects, but are only sensations in our minds. But there are other qualities that do exist objectively, e.g. tastes and sounds. Real sound is nothing but a certain motion of the air.

24 6. Eventually Hylas accepts Locke s full list of secondary qualities, including colours, tastes, smells and sounds. But still, like Locke, Hylas continues to believe that shape, size ( extension and figure ), texture etc. are primary, and exist in the object, not just in a perceiving mind.

25 7. Now the main argument. Philonous tries to show that the same arguments can be applied to (what Locke considers to be) primary qualities, such as figure and extension (shape and size). Philonous appeals to mites. The foot of a mite will seem to be large to a mite, yet tiny to us. So size is subjective.

26 Note the general pattern of argument here: If a quality depends on the observer, i.e. its appearance varies with the type of observer (mite or human) or with the way in which it s perceived, then the quality is subjective, and exists only in the mind. Is this pattern reasonable?

27 8. Also, as we approach and recede from an object, its visible size varies. [Berkeley might have added, but didn t, that a circular pond appears circular only from directly above. From most angles its apparent shape is an ellipse.]

28 9. Also, the same object that is smooth to the naked eye is rough when viewed through a microscope. So textures, a supposed primary quality, also depend on the observer.

29 10. In other words, all qualities turn out to be secondary. There are no primary qualities at all. None which can be supposed to exist independently, without being perceived.

30 11. As a last resort, Hylas appeals to the notion of substratum. The idea of substratum is that the qualities of an object need to belong to something. They need to be properties of something. They re not just a bundle. That something that has the properties is the substratum. You can picture the properties as sewing pins. The substratum is then the pincushion that the pins are stuck into.

31 Substance vs. properties The cheese is a substance, but the holes are not substances. They re just modifications (properties) of the cheese.

32 12.The substratum is not sensible. Hylas says I conclude it exists because qualities cannot be conceived to exist without a support. (p. 103) Later (p. 104) I find that I know nothing of it. Is it not a great contradiction to talk of conceiving a thing which is unconceived? Philonous responds.

33 Another argument 13. no idea nor anything like an idea can exist in an unperceiving substance can anything be like a sensation or idea, but another sensation or idea? The correspondence between ideas and non-mental things strikes many as problematic. For example, the correspondence of propositions to objective facts or states of affairs.

34 Augustinian theism

35 Augustinian theism the view that abstract entities such as universals and possible states of affairs depend for their existence on the divine mind. The ideas are certain archetypal forms or stable and immutable essences of things, which have not themselves been formed but, existing eternally and without change, are contained in the divine intelligence. They neither arise nor pass away, but whatever arises and passes away is formed according to them. (Augustine, De Ideis 2) 35

36 Also accepted by (e.g.): Aquinas Leibniz Robert Adams Thomas Morris and Chris Menzel Alvin Plantinga Even if there were no human intellects, there could be truths because of their relation to the divine intellect. But if, per impossible, there were no intellects at all, but things continued to exist, then there would be no such reality as truth. (Aquinas, De Veritate Q. 1, Article II, Reply). the nature of a circle, and the fact that two and three make five, have eternity in the mind of God (Aquinas, Summa Theologiae Ia, q. 16, a. 7, obj. 1 and reply). 36

37 Problem for Berkeley Minds, or spirits, are (in some sense) mindindependent substances for Berkeley. When God creates humans, for example, he does more than just have an idea. He has to concretise that idea somehow make it active. We aren t just ideas in the mind of God. So why can t there be other mind-independent substances?

38 If we ask Berkeley what makes a mind concrete in a way that ideas are not, what would he say? Something, I know not what? After all, we don t perceive minds, just ideas Can Berkeley have a clear conception of what the mind really is?

39 Problem What s the difference (for Berkeley) between the real world and the possible worlds? It is important not to confuse the actual world with the World. The actual world is a mere specification, a description of a way for things to be. It has only the kind of abstract reality that belongs to a story or a scenario or a computer program. The World, however, is not a description of a way for things to be: it is, so to speak, the things themselves. If it is an individual thing, it has you and me and every other individual thing as parts. (Peter van Inwagen, Metaphysics, 4 th ed., Ch. 6)

40 Locke vs. Berkeley Which theory better explains the facts about sensation that Locke listed? 1. Those lacking some sense organs also lack the corresponding ideas 2. Sensory ideas are involuntary 3. Some sensory ideas (but not imagined ideas) are accompanied by pain. 4. Sensory ideas are orderly and consistent.

41 Phenomenalism a version of idealism (BonJour, p. 125) John Stuart Mill: material objects are nothing but permanent possibilities of sensation, The crucial thing to see is that what Mill and the other phenomenalists are saying is that there are no independently existing objects that are responsible for the possibilities of sensation or the obtainability of sense-data; the actuality and obtainability of sense-data are all there is to the physical or material world. These facts are the bottom line, not explained or explainable by anything further. (p. 126)

42 Phenomenalism Talk of external objects can be systematically translated into talk about actual and possible sense data. A material object is not a mysterious something behind the appearances, i.e. a cause of the sense data. (As Hume argued, such a mind-independent cause of sense data would be unknowable, and in fact the very concept is unintelligible.)

43 Problems with phenomenalism But it is, of course, still abundantly obvious that this conclusion cannot be correct, and so that something must have gone wrong. What explains the agreed fact that sense-data are stable and orderly? For the phenomenalist, it s a brute fact, incapable of being explained. Technical difficulties: In specifying the meaning of a statement about an external object, one cannot appeal to other external objects. It all has to be done using sense-data. Is this possible? What about statements about objects in the distant past? Chisholm s objection involving sensory abnormalities Phenomenalism leads to solipsism?

44 Can RR be defended? Can we have knowledge of causation, other than from experience of both ends? There seem to be examples of this! (E.g. the chemical constituents of stars.) Is IBE (inference to the best explanation) the answer? Requires a priori knowledge?