But, say you, surely there is nothing easier than for me to imagine trees, for instance, in a park [. . .] and nobody by to perceive them. [...] The objects of sense exist only when they are perceived; the trees therefore are in the garden [. . .] no longer than while there is somebody by to perceive them.

Certainly he who can digest a second or third fluxion need not, methinks, be squeamish about any point in divinity.

Many things, for aught I know, may exist, whereof neither I nor any other man hath or can have any idea or notion whatsoever.

All that stock of arguments [the skeptics] produce to depreciate our faculties, and make mankind appear ignorant and low, are drawn principally from this head, to wit, that we are under an invincible blindness as to the true and real nature of things.

How often must I repeat, that I know or am conscious of my own being; and that I myself am not my ideas, but somewhat else, a thinking, active principle that perceives, knows, wills, and operates about ideas?

This perceiving, active being is what I call mind, spirit, soul, or myself. By which words I do not denote any one of my ideas, but a thing entirely distinct from them, wherein they exist, or, which is the same thing, whereby they are perceived; for the existence of an idea consists in being perceived.

It is a mistake, to think the same thing affects both sight and touch. If the same angle or square, which is the object of touch,be also the object of vision, what should hinder the blind man, at first sight, from knowing it?