All bodies that are pleasant to the touch, are so by the slightness of the resistance they make.

Resistance is either to motion along the surface, or to the pressure of the parts on one another: if the former be slight, we call the body smooth; if the latter, soft.

The chief pleasure we receive by feeling, is in the one or the other of these qualities; and if there be a combination of both, our pleasure is greatly increased.

This is so plain, that it is rather more fit to illustrate other things, than to be illustrated itself by an example.

The next source of pleasure in this sense, as in every other, is the continually presenting somewhat new; and we find that bodies which continually vary their surface, are much the most pleasant or beautiful to the feeling, as any one that pleases may experience.