A movement is never anything else but a displacement, a transfer, a change of place undergone by a particle of matter.

What relation of similarity exists between this geometrical fact and a desire, an emotion, a sensation of bitterness?
Far from being identical, these two facts are as distinct as any facts can be, and their distinction is so deep that it should be raised to the height of a principle, the principle of heterogeneity.
This is almost exactly the reasoning that numbers of philosophers have repeated for several years without giving proof of much originality.
This is what I term the metaphysics of concept, for it is a speculation which consists in juggling with abstract ideas.

The moment that a philosopher opposes thought to movement, I ask myself under what form he can think of a "thought," I suppose he must very poetically and very vaguely represent to himself something light and subtle which contrasts with the weight and grossness of material bodies.

And thus our philosopher is punished in the sinning part; his contempt of the earthly has led him into an abuse of abstract reasoning, and this abuse has made him the dupe of a very naive physical metaphor.
At bottom I have not much faith in the nobility of many of our abstract ideas.

In a former psychological study[2] I have shown that many of our abstractions are nothing else than embryonic, and, above all, loosely defined concrete ideas, which can satisfy only an indolent mind, and are, consequently, full of snares.
The opposition between mind and matter appears to me to assume a very different meaning if, instead of repeating ready-made formulas and wasting time on the game of setting concept against concept, we take the trouble to return to the study of nature, and begin by drawing up an inventory of the respective phenomena of mind and matter, examining with each of these phenomena the characteristics in which the first-named differ from the second.