The seventeenth century Cartesian science entails a dualism insofar as the explanation of the mental phenomena is concerned. The mental is characterized as res cogitans having some specific features like consciousness, thoughts, sensations, etc. which are not extended in the spatial world and cannot be explained by the causal laws. The res extensa includes the whole of the physical phenomena extended in space and time. Dualism divides the mental and the physical into two separate realms of explanation. The mental and physical are considered as to separate or unique substances. Substances are independent and irreducible phenomena according to Descartes.

Searle has questioned the very foundations of the Cartesian dualism. He says, “We have an inherited resistance to treating the conscious mind as a biological phenomenon like any other. This goes back to Descartes of seventeenth century. Descartes divided the world into two kinds of substances. Physical substances were the proper domain of science and the mental substances were the property of religion. Something of an acceptance of this division exists even to the present day.”¹ In Searlean sense dualism persists in philosophy of mind because of our Cartesian hangover and our unwillingness to accept mind as a part of nature. The mental life including consciousness, subjectivity (thought, feelings and experiences etc.) has not been accepted as a suitable topic for scientific study. Searle acknowledging these difficulties writes, “There are four features of mental phenomena (consciousness, subjectivity, intentionality, mental causation) which have made them seem impossible to fit into our ‘scientific’ conception of the world as made up of material things. And it is these four features that have made the mind-body problem really difficult and they are so embarrassing that they have led many thinkers in philosophy, psychology and artificial intelligence to say strange implausible things about the mind to incorporate consciousness in the nature and at the same time to demolish the Cartesian structure of dualism… I think the existence of consciousness ought to seem amazing to us. It is easy enough to imagine a universe without it, but if you do you will see that you have imagined a universe that is truly meaningless.”² In this connection, Searle’s basic thrust is to incorporate the mind in the natural world and hence he accepts the interaction between mind and the body. He, besides, admits that mind evolves within the biological nature of man. Hence his theory is called biological naturalism.