November 2, 2009

Does 'The Desk is Black' Express a Proposition?

According to standard versions of subjunctive phenomenalism, such as the version developed by C. I. Lewis, sentences purporting to be about physical objects can be analyzed into long conjunctions of subjunctive conditionals having to do only with sense data and voluntary actions. It's very difficult to actually state these conditionals, but they are supposed to say things like 'if I'm in such and such a condition, and I do X, I will experience Y'.

Alva Noë is not a phenomenalist, but he expresses some similar ideas about the nature of perception. Specifically, Noë argues that perception does not involve the construction of a detailed internal representation of the world but, rather, involves a sort of practical competence in dealing with the world via our sensory apparatus. Thus, for instance, the back half of a tomato which I do not literally see (I see only the surface of the half facing me) is virtually present to me in perception, in the sense that I know how to perceive it directly, given my present position.

One might think that this involves knowledge of Lewis's subjunctive conditionals. However, Noë argues that the know-how involved in perception is non-propositional (Action in Perception, sect. 3.12). This does seem more plausible than Lewis's view because even philosophers have trouble stating the things Lewis says we know. It seems at least somewhat problematic to suppose that someone knows a proposition, especially one that is fairly abstract, without being able to state it. However, it is surely quite common to know how to perform a complicated task without being able to explain exactly how it is done.

What if Noë were a phenomenalist? That is, what happens if we combine this line of thought on perception with the view that perception is constitutive of the physical world? Actually, Berkeley sometimes seems to talk as if something like this is going on:

the proper objects of vision constitute an universal language of the Author of nature, whereby we are instructed how to regulate our actions in order to attain those things that are necessary to the preservation and well-being of our bodies, as also to avoid whatever may be hurtful and destructive of them. It is by their information that we are principally guided in all the transactions and concerns of life (NTV 147).

Elsewhere, however, Berkeley seems to suggest that the knowledge is propositional: "visible ideas are the language whereby the governing spirit on whom we depend, in forms us what tangible things he is about to imprint upon us, in case we excite this or that motion in our bodies" (PHK 44). This line sounds almost identical to the Lewis view.

The most likely interpretation of Berkeley is that (1) he didn't make a distinction between knowledge-that and knowledge-how, at least in this context, and (2) if confronted with such a distinction he would have said that perception furnishes us with both. Any such knowledge for Berkeley will come from sensation by either inference or suggestion (habitual connection) - but knowledge-that and knowledge-how will be in the same boat in that respect.

We might (plausibly) consider revising Berkeley in the direction of Noë to say that perception+suggestion yields only knowledge-how, whereas perception+inference yields only knowledge-that. Taking this line, we should probably call only the former 'perception'. Now, for Berkeley, this is going to be used to define words like 'desk' or 'cherry'. If this is the case, then it is not clear whether statements about desks express propositions at all for, on this view, 'desk knowledge' is really only knowledge-how. If, then, I say 'the desk is black' I may not be expressing a proposition (a potential item of knowledge-that); I may only be somehow verbally conveying knowledge-how.

One might question whether it is possible to verbally convey knowledge-how. Perhaps a better way of stating this is to say that hearers already have knowledge-how which permits them to react appropriately to my saying 'the desk is black'. In other words, utterances of this kind are just part of the perceived world which speakers know how to interact with.

This gets, by a roundabout path, to my suggestion in "The Semantics of Sense Perception" that, according to Berkeley, many words - both in the perceptual language and in human languages - get their 'meaning' from their pragmatics without having any real semantic value. However, on the revision of Berkeley suggested here, the thesis becomes even more radical: none of our physical object talk has semantic value, at all; it is just a language game with some practical value.

Berkeley's real view, I take it, is that physical object terms are indifferently substitutable for any of a large class of actual and possible perceptions, in the appropriate circumstances. The know-how we have, which we are probably unable to put into words, consists in our knowing how to perform the appropriate substitutions. This gives the words of human language, at least, semantic value: they refer to perceptions, or (as Berkeley seems to say in other texts) to structured collections of perceptions.

In sum, on Berkeley's actual view, 'the desk is black' would seem to express a proposition about perceptions (either about individual perceptions, or about a structured collection of actual and merely possible perceptions). However, on the Berkeley-Noë view I have been discussing, stripping perception of propositional content would result in stripping physical object talk of propositional content as well, so that a sentence like 'the desk is black' is just one more perceptual input I know how to react to. The Berkeley-Noë view might be thought to be more plausible than the Berkeley view, at least in that it doesn't involve our having a bunch of propositional knowledge we can't figure out how to state. The price to be paid for this possible improvement is an even more radical departure from so-called 'common sense' philosophy.

Posted by Kenny at November 2, 2009 5:24 PM
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