The problem of the "other" mind looms quietly in the background of this chapter's considerations. The pursuit of the foundation of the independent existence of other objects includes the independent existence of other people. We are not only dreaming but are "dreaming alone." If we are unsure about the status of reality, then we cannot be sure of other people's bodies or their minds.
Though, as Russell points out, there is no way to prove that reality is not just a dream (it is logically possible that you are dreaming as you "read" these words on the computer screen), there is no reason why this should be the case. He writes, "we cannot have reason to reject a belief except on the ground of some other belief." The hypothesis that we are dreaming our experiences is no more plausible than our common-sense hypothesis; we have no further evidence that it is the case. Since there is no ground for other belief, the most natural possibility among possibilities to accept is our common-sense view, belief in an independent external world.
The end of this chapter culminates in a soaring expression of Neo-Platonic ideology. Just as Socrates and Plato believed that a body of truth was intrinsically coherent and that in seeking consistency we reject false beliefs, Russell believes that philosophy "should show us the hierarchy of our instinctive beliefs, beginning with those we hold most strongly, and presenting each as much isolated and as free from irrelevant additions as possible our instinctive beliefs do not clash, but form a harmonious system. There can never be any reason for rejecting one instinctive belief except that it clashes with the others; thus, if they are found to harmonize, the whole system becomes worthy of acceptance." Russell advocates a "systematic organization" of philosophy and of knowledge. He admits that the possibility of error remains for us, but its "likelihood is diminished" by scrutinizing each part of the whole theory.
Russell's formulation that "the whole outer world is nothing but a dream" has been reformulated by subsequent philosophers, including Hilary Putnam, who posited the famous case of a brain in a vat that is "sensitized" by the medium in the vat, but experiences life as we experience it. The idea of a false reality, which is false in the sense that our experiences do not resemble reality as it really is, finds expression in such popular examples as the 1999 motion picture The Matrix.