Central to Searle's analysis of the mind, and to his criticism of materialism, is his view of consciousness as irreducible.
Searle identifies the meaning of reduction as:
The basic intuition that underlies the concept of reductionism seems to be the idea that certain things might be shown to be nothing but certain other sorts of things. Reductionism, then, leads to a peculiar form of the identity relation that we might as well call the "nothing-but" relation: in general, A's can be reduced to B's, iff A's are nothing but B's. [12]
Searle's central point is that consciousness can't be reduced in this way, i.e. that there is no way, in principle, that consciousness can be analysed as "nothing but" something else.
This is a fundamental issue in Objectivism, and on which Searle's position is very similar to Rand.
Rand identifies consciousness as a philosophical axiom, implicit in all facts and not reducible to any other facts.
Existence exists --- and the act of grasping that statement implies two corollary axioms: that something exists which one perceives and that one exists possessing consciousness, consciousness being the faculty of perceiving that which exists. ....Whatever the degree of your knowledge, these two --- existence and consciousness --- are axioms you cannot escape, these two are the irreducible primaries implied in any action you undertake, in any part of your knowledge and in its sum. [13]
An axiomatic concept is the identification of a primary fact of reality, which cannot be analyzed, i.e., reduced to other facts or broken into component parts. It is implicit in all facts and in all knowledge. It is the fundamentally given and directly perceived or experienced, which requires no proof or explanation, but on which all proofs and explanations rest. [14]
Searle identifies two basic aspects of every perception, which he calls (in terminology which Objectivists would regard as unfortunate) "objective physical reality" and "subjective appearance"; by "subjective appearance" Searle is referring to the conscious experience of perception, and so these two terms correspond to Rand's axioms of existence and consciousness. Searle then notes that reduction involves redefining an aspect of "subjective appearance" in terms of the "objective physical reality" which causes it.
We redefine heat and color in terms of the underlying causes of both the subjective experiences and the other surface effects of the underlying causes. "Real" heat is now defined in terms of the kinetic energy of the molecular movements, and the subjective feel of heat that we get when we touch a hot object is now treated as just a subjective appearance caused by heat, as an effect of heat. It is no longer part of real heat. A similar distinction is made between real color and the subjective experience of color. [15]
Searle's basic argument for the irreducibility of consciousness is that consciousness is subjective experience, and so the above pattern of reduction can't be applied to it.
It is a general feature of such reductions that the phenomenon is defined in terms of the "reality" and not in terms of the "appearance". But we can't make that sort of appearance-reality distinction for consciousness because consciousness consists in the appearances themselves. [16]
As I mentioned, Objectivists would regard the terminology of this argument as unfortunate. The terminology is strongly based on the premise of representationalism, the idea that we are conscious, not of entities in the outside world, but of representations, or appearances, that our mind creates of these entities [17]. However, the substance of Searle's argument does not depend on representationalism. Searle's argument is based on the recognition of our conscious experiences as an irreducible aspect of all perception --- which is equivalent to Rand's point about the axiomatic status of consciousness.
Searle does not (and Rand would not) deny that it is possible to causally explain the existence of the faculty of consciousness; on the contrary, as we see in the quote above from p. 1, he stresses that mental phenomena are caused by neurophysiological processes. But these neurophysiological processes cause mental phenomena, they do not --- and, in principle, can not --- constitute mental phenomena. And it is a self-evident, directly observable fact about mental phenomena that they are active, causally efficacious. The existence of mental phenomena can be causally explained by reference to neurophysiological structures and processes, but specific mental phenomena can't be causally reduced to neurophysiological processes; mental processes have their own causal powers, which can not be analysed as the sum of the causal powers of neurophysiological processes. (On this point, unfortunately, Searle is not at all clear, and at some points he states that such causal reduction is possible. I regard this as the most serious weakness of Searle's book, and I will discuss it at length below.)
Another central aspect of Searle's analysis of the mind is his distinction between those attributes of an entity which are intrinsic, and those which are "observer-relative".[18] The neurophysiological properties of the brain, and its mental properties, are both intrinsic to the brain.
In contrast, all computational or information-processing descriptions of processes in the brain (except when the computation is done consciously) are completely observer-relative.
To say that something is functioning as a computational process is to say something more than that a pattern of physical events is occuring. It requires the assignment of a computational interpretation by some agent. Analogously, we might discover in nature objects that had the same sort of shape as chairs and that could therefore be used as chairs; but we could not discover objects in nature that were functioning as chairs, except relative to some agents who regarded them or used them as chairs.[19]
Computational interpretations can be --- in some contexts, appropriately --- assigned to brain processes; in the same way, such interpretations can be assigned in some contexts to any other physical process. But such interpretations are not describing facts about the process, independent of an observer; they are describing an observer's way of understanding the process.
Searle's main criticism of the orthodoxy of modern cognitive science is that it is based on treating brain processes as intrinsically computational. Writers such as Dennett or Churchland get the nature of our mental life precisely backwards: computation --- which, at most, is an observer-relative feature of brain processes --- is treated as if it were intrinsic; whereas consciousness and intentionality --- which are intrinsic facts about the brain --- are either denied or treated as if they were observer-relative (as in Dennet's intentional stance").