Berkeley,
George (1685-1753):
Irish philosopher. Became Bishop of Cloyne in 1734.
"XVIII. The existence of external bodies wants proof. But though it were possible that solid, figured, moveable substances may exist without the mind, corresponding to the ideas we have of bodies, yet how is it possible for us to know this? Either we must know it by sense or by reason. As for our senses, by them we have the knowledge only of our sensations, ideas, or those things that are immediately perceived by sense, call them what you will: but they do not inform us that things exist without the mind, or unperceived, like to those which are perceived. This the materialists themselves acknowledge. It remains therefore that if we have any knowledge at all of external things, it must be by reason, inferring their existence from what is immediately perceived by sense. But I do not see what reason can induce us to believe the existence of bodies without mind, from what we perceive, since the very patrons of matter themselves do not pretend, there is any necessary connection betwixt them and our ideas. I say, it is granted on all hands (and what happens in dreams, frenzies, and the like, puts it beyond dispute) that it is possible we might be affected with all the ideas we have now, though no bodies existed without, resembling them. Hence it is evident the supposition of external bodies is not necessary for producing our ideas; since it is granted they are produced sometimes, and might possibly be produced always, in the same order we see them in at present, without their concurrence."
Treatise Concerning the Principles of Human Knowledge. George Berkeley. (1710).