The sensitive consciousness is thus revealed to us as composed of three elements; a permanent self, having a sensitive organism extended in space, and with successive affections of that organism taking place in time. None of these elements, apart from the rest, can he presented or represented in consciousness; and the distinction between sense and intelligence is thus verbal only, not real, constituting, like the concave and convex circumference of a circle, different sides of the same consciousness, but incapable in any act of thought of being considered apart from each other.
In the words of Sir William Hamilton “It is manifestly impossible to discriminate with any rigour sense from intelligence. Sensitive apprehension is in truth only the recognition by intelligence of the phenomena presented in or through its organs. The proper sensibles—smell, taste, sound, colour, and tactual sensation—all belong to the class commonly called secondary qualities of body; which are in reality affections of the nervous organism, which have no resemblance to any attribute of inorganic bodies.
It is true that, in their normal state, they are excited by the presence of such bodies; but that in themselves, as apprehended, they are states of the nervous organism, and not qualities of other bodies, is evident from the fact that they may be abnormally called into existence by any circumstance which produces the appropriateness.
What, then, it may be asked, is the nature of our sensations as thus described? Are they affections of mind, or of body, or of both ? On the one hand, consciousness, in all its modes, seems manifestly to be a state of mind. On the other hand, sensitive consciousness appears with the concomitant condition of extension, which is an attribute of body. The general voice of modern philosophers has pronounced that sensations, as such, belong to mind, and not to body.
This is asserted both by those who admit and by those who deny the existence of perceptible primary qualities of body in addition to the mental sensation. And rightly, so long as by body is meant something distinct from our own organism; but wrongly, or at least inaccurately in language, so long as no distinction is made between body as brute matter and body as part of a sentient being.
***Excerpt from Henry Longueville Mansel, B.d.. Metaphysics or the philosophy of consciousness