Locke - An Essay Concerning Human Understanding (Selections)
Some further considerations concerning our Simple Ideas of Sensation
1. Positive ideas from privative causes. Concerning the simple ideas of Sensation, it is to be considered,- that whatsoever is so constituted in nature as to be able, by affecting our senses, to cause any perception in the mind, doth thereby produce in the understanding a simple idea; which, whatever be the external cause of it, when it comes to be taken notice of by our discerning faculty, it is by the mind looked on and considered there to be a real positive idea in the understanding, as much as any other whatsoever; though, perhaps, the cause of it be but a privation of the subject.
2. Ideas in the mind distinguished from that in things which gives rise to them. Thus the ideas of heat and cold, light and darkness, white and black, motion and rest, are equally clear and positive ideas in the