In that case we should be obliged to set aside the question as one already decided.

Where everything is homogeneous, there is no distinction to be drawn.

But this hypothesis is, as we all know, falsified by observation.

The whole body of the knowable is formed from an agglomeration of extremely varied elements, amongst which it is easy to distinguish a large number of divisions.

Things may be classified according to their colour, their shape, their weight, the pleasure they give us, their quality of being alive or dead, and so on; one much given to classification would only be troubled by the number of possible distinctions.
Since so many divisions are possible, at which shall we stop and say: this is the one which corresponds exactly to the opposition of mind and matter?
The choice is not easy to make; for we shall see that certain authors put the distinction between the physical and the mental in one thing, others in another.