Despite this, I can’t go so far as to conclude that mind poses some insurmountable barrier to materialism. There are two reasons. The first is, frankly, more a sociological observation than an actual argument. Science has, since the seventeenth century, proved remarkably adept at incorporating initially alien ideas (like electromagnetic fields) into its thinking. Yet most people, apparently including Nagel, find the resulting science sufficiently materialist. The unusual way in which physicists understand the weirdness of quantum mechanics might be especially instructive as a crude template for how the consciousness story could play out. Physicists describe quantum mechanics by writing equations. The fact that no one, including them, can quite intuit the meaning of these equations is often deemed beside the point. The solution is the equation. One can imagine a similar course for consciousness research: the solution is X, whether you can intuit X or not. Indeed the fact that you can’t intuit X might say more about you than it does about consciousness.In that prior post I argued that the scientific explanation for consciousness, which can be cast in terms of a generalized function that explains consciousness (X) in terms of some set of factors, necessarily falsifies the nature of consciousness by turning it from the constitutor of the world into just another thing in the world. Even if this project is in some sense successful, it will not touch the consciousness Y that underwrites the scientific explanation of consciousness X in the first place. Orr's point in his first paragraph is irrelevant. It doesn't matter whether we intuit X or satisify ourselves with an equation about X ala quantum mechanics. It is the form of science itself that vitiates the possibility of a thoroughgoing scientific explanation of consciousness.
And this brings me to the second reason. For there might be perfectly good reasons why you can’t imagine a solution to the problem of consciousness. As the philosopher Colin McGinn has emphasized, your very inability to imagine a solution might reflect your cognitive limitations as an evolved creature. The point is that we have no reason to believe that we, as organisms whose brains are evolved and finite, can fathom the answer to every question that we can ask. All other species have cognitive limitations, why not us? So even if matter does give rise to mind, we might not be able to understand how.
A scientific equation divides and unifies. It divides reality into a set of factors (force, mass, acceleration, brain chemistry, photons, etc.) and then reunifies them in the equation. The ground of that reunification necessarily transcends the factors that are unified. This is not a mystical point. It merely says that if we are going to split things into force, mass and acceleration, and then say F = ma, it can't be either force, mass or acceleration that synthesizes these factors in the unity (to use Kant-speak) of the equation, since the equation hypothesizes them as factors of division rather than unity. The unifiying synthesis, of course, happens in the mind of the scientist, which is entirely non-problematic in normal scientific investigation. It becomes problematic when this same method is used in an attempt to understand consciousness itself, for then the attempt is made to include consciousness both as a factor of division ( as in the equation consciousness X = some function of brain chemistry, photons, neurons, etc) and as the ground of the unifying synthesis (as consciousness Y of the scientist constructing the theory). This is to attempt to cross the border that Kant identified in his delineation of the modern understanding of the mind. And Kant argued that this border can never be crossed because whenever we try to cross it, we simply push it further in front of us. Any scientific explanation implies a consciousness that transcends the factors of explanation and serves as the synthesizer of them into the unity of explanation. As soon as we try to understand consciousness scientifically, we turn it into a scientific factor that is transcended by the scientific mind analyzing it. This may be useful and rewarding for some purposes, but it will by the nature of the case leave the most signficant aspects of consciousness untouched.
As for Orr's second paragraph, with Kant we can do more than idly speculate concerning cognitive limitations that evolution might have imposed on us. We can analyze the nature of cognition, and scientific investigation, a priori and show that their very natures preclude a scientific understanding of consciousness, whatever evolution may or may not have done for us.