Meditations on First Philosophy (1641)
In this, the founding text of the modern philosophy of mind, Descartes argues that there is a "real distinction" between the mind and the body. They are, he says, distinct "substances". We can imagine ourselves existing without a body but there is one thing whose existence cannot be doubted: the thing that does the doubting. Despite being very different kinds of stuff, the mind and body nonetheless interact. The site of that interaction, Descartes believes, is the pineal gland (a small gland near the centre of the brain).
Spinoza rejects the premises of Cartesian dualism. For him, mind (or thought) and body (or matter) are not distinct types of stuff but rather "attributes" of a single substance, which he calls deus sive natura ("God or nature").
Select Works (1886)
Thomas Henry Huxley
In an essay entitled "On the Hypothesis that Animals Are Automata, and Its History", Huxley, who once described himself as "Darwin's bulldog", defends the doctrine of "epiphenomenalism". "Our mental conditions," Huxley writes, "are simply the symbols in consciousness of the changes which take place automatically in the organism." In other words, he accepts the Cartesian claim that mind and body are distinct but he rejects the idea that there is any sort of causal interaction between them. On the contrary, the mind is causally inert - it is but an emanation of the brain that has no effect on it.…