Descartes' view on the differentiation between mind and body gave rise to many reflections on the interaction between these seemingly distinct substances. Examining the correlations between Princess Elizabeth of Bohemia it is evident that Descartes himself struggled to plausibly identify the interaction between the mental and the material in relation to causality. This essay will investigate Elizabeth's questions about the causal relationship between mind and body by explaining and investigating Descartes' distinction between the mental and the physical as separate substances, Elizabeth's concern in relation to the problem of interaction, and Descartes' response to these concerns . there are two fundamental types of distinct substances: material (physical thing) and mental (incorporeal, thinking thing) is a philosophical position in line with the claims of theology that believe that an independent sphere of existence, separate from that of the physical world, is occupied by immortal spirits (Hart 1996) and therefore may have been developed to prove the existence of God. Describing the mind as a “thinking, non-extended thing” and the body as an “extended, non-thinking thing”, Descartes insists on his sixth Meditation on the fact that even after a great bodily change, a material substance remains itself only in an altered form. . As such it follows that the basis of what makes this thing what it is must be based on a distinct and non-extended substance. Descartes goes on to explain the possibility that the mind exists without the form of a material body, as a substance whose essence is thought, and therefore undoubtedly distinct from the physical. Even though they are both ontologically separate substances, the essential... the center of the paper... ole. As Descartes begins in The Principles, Part 1: “But we also experience within ourselves some other things, which need not be referred either to the mind alone or to the body alone. This arises, as will be said in its place, from the close and intimate union of our mind with the body". For example, the movement of an eye can produce modes of sensation in the mind, and it is that combination of the mental and physical in humans that causes the perception of a chair (or whatever sight one might see). Since mind acting on the body through voluntary action and body on the mind through both perception and sensation are constantly experienced, an interaction between the mental and the material is obvious. Descartes argues that humans possess the primordial notion of substantial union, yet it is often baffling and misapplied..•