EXTENSION, SOLIDITY, MOBILITY, or the power of being moved; which by our senses we receive from body: PERCEPTIVITY, or the power of perception, or thinking; MOTIVITY, or the power of moving: which by reflection we receive from OUR MINDS.
I crave leave to make use of these two new words, to avoid the danger of being mistaken in the use of those which are equivocal.
To which if we add EXISTENCE, DURATION, NUMBER, which belong both to the one and the other, we have, perhaps, all the original ideas on which the rest depend.

For by these, I imagine, might be EXPLAINED the nature of colours, sounds, tastes, smells, and ALL OTHER IDEAS WE HAVE, if we had but faculties acute enough to perceive the severally modified extensions and motions of these minute bodies, which produce those several sensations in us.

But my present purpose being only to inquire into the knowledge the mind has of things, by those ideas and appearances which God has fitted it to receive from them, and how the mind comes by that knowledge; rather than into their causes or manner of Production, I shall not, contrary to the design of this Essay, see myself to inquire philosophically into the peculiar constitution of BODIES, and the configuration of parts, whereby THEY have the power to produce in us the ideas of their sensible qualities.

I shall not enter any further into that disquisition; it sufficing to my purpose to observe, that gold or saffron has power to produce in us the idea of yellow, and snow or milk the idea of white, which we can only have by our sight without examining the texture of the parts of those bodies or the particular figures or motion of the particles which rebound from them, to cause in us that particular sensation, though, when we go beyond the bare ideas in our minds and would inquire into their causes, we cannot conceive anything else to be in any sensible object, whereby it produces different ideas in us, but the different bulk, figure, number, texture, and motion of its insensible parts..