This is the third in a series of posts on Thomas Nagel's Mind and Cosmos (Oxford 2012). The first is an overview, and the second addresses Nagel's reason for rejecting theism. This post will comment on some of the content in Chapter 4, "Cognition."
In Chapter 4, Nagel tackles the topic of reason, both theoretical and practical. The emphasis is on theoretical reason, with practical reason receiving a closer treatment in the following chapter entitled "Value."
We have already seen that consciousness presents a problem for evolutionary reductionism due to its irreducibly subjective character. (For some explanation of this irreducibly subjective character, see my Like, What Does It Mean?)
'Consciousness' taken narrowly refers to phenomenal consciousness, pleasures, pains, emotions, and the like, but taken widely it embraces also thought, reasoning and evaluation. Sensory qualia are present in nonhuman animals, but only we think, reason, and evaluate. We evaluate our thoughts as either true or false, our reasonings as either valid or invalid, and our actions as either right or wrong, good or bad. These higher-level capacities can be possessed only by beings that are also conscious in the narrow sense. Thus no computer literally thinks or reasons or evaluates the quality of its reasoning imposing norms on itself as to how it ought to reason if it is to arrive at truth; at best computers simulate these activities. Talk of computers thinking is metaphorical. This is a contested point, of course. But if mind is a biological phenomenon as Nagel maintains, then this is not particularly surprising.
What makes consciousness fascinating is that while it is irreducibly subjective, it is also, in its higher manifestations, transcensive of subjectivity. (This is my formulation, not Nagel's.) Mind is not trapped within its interiority but transcends it toward impersonal objectivity, the "view from nowhere." Consciousness develops into "an instrument of transcendence that can grasp objective reality and objective value." (85) Both sides of mind, the subjective and the objective, pose a problem for reductive naturalism. "It is not merely the subjectivity of thought but its capacity to transcend subjectivity and to dsiscover what is objectively the case that presents a problem." (72)
Exactly right! One cannot prise apart the two sides of mind, segregating the qualia problem from the intentionality problem, calling the former 'hard' and imagining the latter to be solved by some functionalist analysis. It just won't work. The so-called Hard Problem is actually insoluble on reductive naturalism, and so is the intentionality problem. (Some who appreciate this go eliminativist -- which is a bit like getting rid of a headache by blowing one's brains out.)
The main problem Nagel deals with in this chapter concerns the reliability of reason. Now it is a given that reason is reliable, though not infallible, and that it is a source of objective knowledge. The problem is not whether reason is reliable as a source of knowledge, but how it it is possible for reason to be reliable if evolutionary naturalism is true. I think it is helpful to divide this question into two:
Q1. How can reason be reliable if materialist evolutionary naturalism is true?
Q2. How can reason be reliable if evolutionary naturalism is true?
Let us not forget that Nagel himself is an evolutionary naturalist. He is clearly a naturalist as I explained in my first post, and he does not deny the central tenets of the theory of evolution. His objections are to reductive materialism (psychophysical reductionism) and not to either naturalism or evolution. Now Nagel is quite convinced, and I am too, that the answer to (Q1) is that it is not possible for reason to be relied upon in the manner in which we do in fact rely upon it, if materialism is true. The open question for Nagel is (Q2). Reason is reliable, and some version of evolutionary naturalism is also true. The problem is to understand how it is possible for both of them to be true.
Now in this post I am not concerned with Nagel's tentative and admttedly speculative answer to (Q2). I hope to take that up in a subsequent post. My task at present is to understand why Nagel thinks that it is not possible for reason to be reliable if materialism is true.
Suppose we contrast seeing a tree with grasping a truth by reason.
Vision is for the most part reliable: I am, for the most part, justified in believing the evidence of my senses. And this despite the fact that from time to time I fall victim to perceptual illusions. My justification is in no way undermined if I think of myself and my visual system as a product of Darwinian natural selection. "I am nevertheless justified in believing the evidence of my senses for the most part, because this is consistent with the hypothesis that an accurate representation of the world around me results from senses shaped by evolution to serve that function." (80)
Now suppose I grasp a truth by reason. (E.g., that I must be driving North because the rising sun is on my right.) Can the correctness of this logical inference be confirmed by the reflection that the reliability of logical thinking is consistent with the hypothesis that evolution has selected instances of such thinking for accuracy?
No, says Nagel and for a very powerful reason. When I reason I engage in such operations as the following: I make judgments about consistency and inconsistency; draw conclusions from premises; subsume particulars under universals, etc. So if I judge that the reliability of reason is consistent with an evolutionary explanation of its origin, I presuppose the reliability of reason in making this very judgement. Nagel writes:
It is not possible to think, "reliance on my reason, including my reliance on this very judgment, is reasonable because it is consistent with its having an evolutionary explanation." Therefore any evolutionary account of the place of reason presupposes reason's validity and cannot confirm it without circularity. (80-81)
Nagel's point is that the validity of reason can neither be confirmed nor undermined by any evolutionary account of its origins. Moreover, if reason has a merely materialist origin it would not be reliable, for then its appearance would be a fluke or accident. And yet reason is tied to organisms just as consciousness is. Nagel faces the problem of explaining how reason can be what it is, an "instrument of transcendence" (85) and a "final court of appeal" (83), while also being wholly natural and a product of evolution. I'll address this topic in a later post.
Why can't reason be a cosmic accident, a fluke? This is discussed in my second post linked to above, though I suspect I will be coming back to it.
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