Searle is aware that the relation between brain and consciousness cannot be truly exhausted by the causal categories. As Searle puts it “…there are enormous empirical mysteries about how brain works in detail, there are no logical, or philosophical or metaphysical obstacles to accounting for the relation between the mind and the brain in terms that they are quit familiar to us from the rest of nature”.⁷ The brain-mind relationship, however, has to be empirically explained. This is the task of neurophysiology. Neuro-physiologists believe in the scientific study of each aspect of the brain processes in order to eliminate the mystery of consciousness. Most of the Cartesian like Hartfield try to bring out the causal interactionism between mind and body. As Hertfeild writes, “… he [Descartes] generally treated mind and body relation as mystery. When he explained the relation between bodily state and its mental effect (or vice-versa), he appealed to the ‘Institution of the nature’ which in effect is a relationship established by God and such as to account for the fact that an “appropriate” mental occurs on occasion of a given bodily configuration.⁸  Searle follows Descartes in not denying that there is a deep mystery in the mind-body relation. However, we may try we cannot finally resolve the mystery.

Searle’s Cartesian legacy consists in that though biological naturalism rejects the Cartesian dualism, still it holds that consciousness is something independent of the brain processes and cannot be fully reduced to the neurological processes. Like Descartes, Searle also shares the view that consciousness pertains to the realm of the mental. For him, consciousness cannot be reduced to the physical phenomena. Searle decides, consciousness has such features like intentionality, rationality, freewill, subjectivity, etc. Thus Searle’s biological naturalism sounds very much Cartesianism.