The realist, John Locke, set the stage for the idealist, George Berkeley. Locke believed in a material substratum that upholds the qualities of physical objects. B. Epistemological dualism . Locke believed in the distinction between the knower and the thing known. But he was not a naive dualist, for he did not believe that we know objects in the world directly, but rather mental representations of them.
Ideas exist only in minds.
He can, with justice, claim to have common sense on his side, for the common sense view is that things are immediately perceived. To deny his argument we must take the unusual position that we do not immediately perceive things themselves but, after the fashion of the dualists, only representations of them. 1. explain how two so dissimilar substances can relate to each other 2. explain how mind can know reality if reality is so utterly unlike mind and its ideas. Berkelean idealism overcomes the doubt that our ideas correctly represent the world. But of course he couldn t talk about it for, as that which underlies qualities, it is devoid of them.