This lands us to eighteenth and nineteenth century materialism, namely, the belief that what is real in nature is matter, in time and in space and with inertia.
Evidently a distinction in quality has been presupposed separating off some perceptions due to touch from other perceptions.

These touch-perceptions are perceptions of the real inertia, whereas the other perceptions are psychic additions which must be explained on the causal theory.

This distinction is the product of an epoch in which physical science has got ahead of medical pathology and of physiology.
Perceptions of push are just as much the outcome of transmission as are perceptions of colour.

When colour is perceived the nerves of the body are excited in one way and transmit their message towards the brain, and when push is perceived other nerves of the body are excited in another way and transmit their message towards the brain.

The message of the one set is not the conveyance of colour, and the message of the other set is not the conveyance of push.