"Berkeley discusses the view that we must distinguish the act of perceiving from the object perceived, and that the former is mental while the latter is not. His argument against this view is obscure, and necessarily so, since, for one who believes in mental substance, as Berkeley does, there is no valid means of refuting it. He says: “That any immediate object of the senses should exist in an unthinking substance, or exterior to all minds, is in itself an evident contradiction.” There is here a fallacy, analogous to the following: “It is impossible for a nephew to exist without an uncle; now Mr. A is a nephew; therefore it is logically necessary for Mr. A to have an uncle.” It is, of course, logically necessary given that Mr. A is a nephew, but not from anything to be discovered by analysis of Mr. A. So, if something is an object of the senses, some mind is concerned with it; but it does not follow that the same thing could not have existed without being an object of the senses."