The actual expression "Ghost in the Machine" was coined by Gilbert Ryle in his seminal 1949 book The Concept of Mind, in which he demolished what he called the orthodox theory then current that there was a mind inside people, sitting inside their bodies and observing what their senses fed into the brain: that is, the cartesian dualist picture.

He also spoke of it as the horse inside the locomotive. The general idea is that the thing we can see apparently doing the work (the brain, the locomotive) is believed to be fundamentally insufficient to do what it seems to be doing, so something else is postulated inside it. Both of his expressions were intended to point up the absurdity of this.

Ryle's demolition of this idea was so thorough that it is almost impossible for any philosopher or scientist to be taken quite seriously if they still maintain the division.

Arthur Koestler boldly entitled a book The Ghost in the Machine, but that's rather the point, he was not a very good philosopher.

However, Sir Karl Popper and Sir John Eccles did maintain an overt form of dualism, and their joint book The Self and its Brain espoused this. Popper defended the logic of different categories of "world", while the physiologist Eccles tried to connect mind and brain in modern terms.

Today the main successor of Ryle in the strongly anti-cartesian line is Daniel Dennett, especially in his Consciousness Explained. Most of his opponents who hold that there exist some kinds of true mental fauna (often called qualia) would nevertheless agree that the mental is a property of the brain, not of a separate ghostly Mind sitting in a "cartesian theatre".