Saturday, July 17, 2010

The Virtues of Functionalism

As I see it, functionalism about the mind (the view that all mental states can be defined purely in terms of a relation between sensory inputs and behavioral outputs), has three primary benefits. That is, there are three primary reasons a contemporary philosopher, with a physicalist bent and a strong respect of science, may want to accept it. They are the following:

(1) Functionalism, unlike the identity-theory of mind, preserves multiple realizability. What this means is that different neural structures could, in principle, realize one and the same type of mental state. This is important because it seems, for example, implausible that lower animals which seem to be conscious, but lack our particular neural structure, could not realize a mental state like pain. But if functionalism is true, all that's needed to preserve the same type of mental state is to have the same type of sensory inputs and behavioral outputs.

(2) Functionalism is compatible with a strong supervenience physicalism. The reason for this is that, if mental states are defined purely in terms of a relation between sensory inputs and behavioral outputs, then mental states will always and only supervene on those types of facts, which are (obviously) purely physical. So, functionalism is well-grounded in the physical world, and indeed dependent upon it.

(3) Functionalism makes sense from an evolutionary standpoint. Unlike dualism, forms of epiphenomenalism, and even simple property-dualism, functionalism has a plausible evolutionary story. If mental states really do function as a means of sensory inputs eventually having specific behavioral outputs, then its obvious why and how they could have evolved: Evolution selects for behavior, and if some type of mental state provided for the necessary means to achieve that survival-beneficient behavior, it would be selected for and, well, here we are today.

Friday, July 16, 2010

Perception, Illusion, and Naive Realism


Consider the image to the right. First, picture it as a duck. Now, as a rabbit. This image, made famous by the 19th century psychologist Joseph Jastrow, was invented to make a point about perception: That what we percieve is not only due to sensuous experience, but it is also due, in part, to our own mental activity. This point about psychology is however not as interesting as the philosophical implications that follow from it. E.g., that naive realism is false, and indirect realism (construed essentially as Kant stated it) is true. Let's take a look at how this line of thinking works.

Naive realism is the view that we percieve objects directly, where direct perception is taken to mean that there is no mediating representation, cognitive interpretation, or what-have-you that cuts us off from the thing-in-itself. What we percieve, for the naive realist, is essentially what would be there even if no one were there to percieve it (e.g., the thing-in-itself). In contrast, the claim of the indirect realist is that we always and only percieve a representation of a thing ("representation" being construed in various ways). That is, the object of our perception only is what it is, at least in part, because of our cognitive contribution to it, whether by way of a conceptual scheme, the fact that we only percieve Lockean secondary properties, or whatever.

So how does our beloved duck-rabbit bear on this debate? It's quite simple really: Consider carefully the nature of the optical illusion you just experienced. The raw sense data involved in the perception are identical both in the case of seeing the rabbit in the image (call this an "A-type" experience), and seeing the duck in the image (call this a "B-type" experience). Yet, the experiences (differentiating experiences by their differing qualia) are emphatically not identical. What follows is that, at least in this case, part of what constitutes a given experience as either A-type or B-type is your mode of cognition at that particular moment, not merely the object affecting the senses. If we percieved things directly, then the object itself would be sufficient to determine the type of experience we were having, yet it seems obvious that this isn't the case. Thus, we cognitively contribute to the world in such a way that we can have identical sensory-inputs, yet totally different mental-state outputs. It follows that direct, or naive, realism is false. Put in terms of an argument, this thought is as follows:

(1)An experience is individuated by either (a) the raw sense data involved, or (b) the conjunction of the raw sense data and the cognition involved.
(2) The experience of the duck-rabbit as either a rabbit, or a duck, cannot be individuated merely by the sense data involved.
(3) Therefore, the experience of the duck-rabbit as either a rabbit, or a duck, is individuated by the conjunction of raw sense data and our cognition.

Now here's a further question: What exactly is the nature of the cognition involved in this particular instance? I think the answer is that it is intentionality that is our cognitive contribution. What I mean to say is that, whenever we have an experience, the experience is never a bare experience, but it is always of something. The "of something" is key because it shows that all experience has intentionality embedded in it. We always take ourselves to be having an experience of a particular sort of object, but the idea that it is a particular sort of object shows that we take our experiences to have content. Take the following example: In the 1st century A.D., the wrist was considered to be a part of the hand. Nowadays, we view it as distinct (for us, the hand ends at the wrist). Now take a person from the 1st century, and the 21st century, and show them a picture of a hand and a wrist. The former will have the experience of seeing a hand, the latter will have a different experience, e.g. that of seeing a hand and a wrist. Two experience-types, one raw sense data. And what differentiates the two types? What they take their experience of the picture to be of, that is, the content of the experience provided by (you guessed it) our own cognition.

(As a sort of side-note, another interesting thing about the duck-rabbit experiment is this: A group of psychologists showed the picture to people on Easter Sunday, the vast majority of which percieved the picture as being of a rabbit, not a duck. Conversely, when participants were shown the picture during other parts of the year, such as October, most of them saw it as a duck. This shows that the type of experience we end up having is not only a function of our own cognition, but the context in which we find ourself doing the percieving.)

There's an interesting analogue here, I think, with Kuhn's idea of the so-called "theory-ladenness of observation" in science. Here we have what you might call the concept-ladenness of perception. As Kant said, we can only percieve that which we're able to cognize, and not vice versa. Of course, there are a number of sticky issues that make this whole debate not so simple, but I think this example is a good starting point for grasping the general idea of cognitive representation.

Sunday, July 11, 2010

The Laws of Logic: Contingent or Necessary?

One of the debates in philosophical logic is whether the laws of logic hold contingently or necessarily. One of the possible motivations for thinking that they hold contingently is that they bear some sort of analogue to physical laws. Whereas physical laws express regularities in nature, logical laws might express regularities in human language, or our cognitive structure. So, just as the regularities we see in nature are generalized into universal laws by induction, so regularities in human reasoning are generalized into universal laws.

To me, though, this is a false picture. There are several irremediable issues, as I see it, with the contingent view of logical laws. I think that the necessity view of logical laws, properly expressed, more fully captures their nature. But, before addressing what my own view is, I want to take a look at what the specific issues are in regard to the contingent view (hereafter simply CV).

The first issue is that CV seems to be self-refuting in a way. The reason is that, whenever you try to establish a proposition, you assume that various logical laws hold necessarily. Consider the following argument:

(1) If Reason X, then CV.
(2) Reason X.
(3) Therefore, CV.

Most arguments seeking to establish the truth of CV would take that form or something like it (where "Reason X" might be the contingency of our conceptual scheme, quantum weirdness, or whatever). But, if CV is true, then any such argument (which will assume such laws as implication, non-contradiction, transitivity, and the like) will hold contingently. That is, it will be a contingent truth that the laws of logic hold contingently, which seems counter-intuitive if not outright self-refuting. Further, if the laws of logic are contingent contingently, then they could have been necessary de dicto, but aren't. Which leads to the further, extremely counter-intuitive conclusion that the S5 axiom of modal logic is false (that is, If possibly necessarily P, then necessarily P). So we're already in a muck of circularity, contradiction, and outright confusion.

The next issue with CV is with the inability to concieve of, or describe, a world in which our logical laws did not hold. Try and concieve of a world in which something both can be an A, and not an A, in the same way at the same time. It seems literally impossible. But I don't think the impossibility arises from our lack of ability to picture it (due to our limited experience or whatever), but it rather arises from the fact that such a statement is literally meaningless. The statement "Something is both an A and not an A" doesn't describe any state of affairs, and thus is about nothing. But if we can't even speak meaningfully about such a possible world, why should we take the thesis of CV seriously?

This leads us to my view. I think the correct view of the laws of logic is that (a) they are necessary, and (b) analytically necessary. What exactly I mean by analytically necessary I'll address in a moment, but I first want to look at the aforementioned apparent analogue between physical and logical laws.

I think the analogue is false for the following reason: When we observe regularities in nature, and proceed to generalize them into laws, we do so because of inductive evidence along with the assumption of the uniformity of nature. But, there's nothing inherent in the evidence itself that suggests the regularity just is or implies the physical law (as Hume pointed out, correctly, in his discussion of constant conjunction). This differs from logical laws in that it doesn't seem they are generalizations of observation, but rather generalizations of meaning. To see this, consider the following comparison between the law of gravity and the law of transitivity:

When we continually observe that things fall, objects are attracted to eachother, and the like, we take the inductive leap and say "This is a physical law, the law of gravity". But (again, as Hume pointed out) there's nothing inherent in the meaning of X number of objects falling and/or being attracted to one another that necessarily implies such a law. The law is just a deductively unwarranted assumption, which functions more pragmatically than evidentially. So, again, there's nothing inherent in the meaning of our observations that just means "the law of gravitation".

But what about in the case of a logical law like that of transitivity (A->B, B->C, :. A->C)? In this case, it can be seen that part of what we mean by the conjunction of "A->B" and "B->C" just is "A->C". And this is what I meant by all logical laws being analytically true. For any given logical law, upon reflection we can see that it holds in virtue of its meaning, not in virtue of its use or anything else. Another way to put this would be to say that all logical laws are merely tautologies. To take another example, consider the law of non-contradiction. When we assert "A", part of what we mean by "A" is just "~~A". And thus we express such a tautology as the "law" "A cannot be both A and not A".

It can be seen that my view differs from a more Platonic view where the laws of logic are necessary de re (in virtue of abstractly existing objects and the relations they bear to one another). But rather, all logical laws are true de dicto. And hence, if my view is true, there are no possible worlds in which, say, modus ponens could be invalid without the meaning of modus ponens also changing. Suffice it to say, the contingent view is false, and the necessity view far more plausible.

Wednesday, July 7, 2010

Meaning and Truth-Conditionality

One common theory of meaning is this: To know a statement's meaning is to know the conditions under which the statement would be true. So, for example, to know the meaning of the statement "Jones will throw the ball" is to know that such a statement would be true if and only if the event "Jones throwing the ball" obtained. Seems plausible enough.

But there's an obvious difficulty with such a theory. If to know some statement S's meaning one need only know S's necessary and sufficient conditions, how do you explain the fact that the antecedents and consequents of many biconditionals obviously differ in meaning? For example, in the biconditional "I will go to sleep if and only if I take the pills", the statement "I will go to sleep" has "Going to sleep" as its necessary and sufficient conditions, but so does "Taking the pills". So, they both have the same truth-conditions, yet differ in meaning. It's true that they are logically equivalent, but they can't be (by reductio) meaning-equivalent. It follows that truth-conditionality doesn't fully explain the curious explanandum of meaning.

Note: It may be objected that the biconditional "P<->Q" is reducible merely to "(P->Q)&(Q->P)". But this is false. Having the same truth conditions, logically, "P<->Q" is also equivalent to "Q<->P", and (of course) the tautology always holds "P<->P".