space is also the one of which we have the most difficulty in ridding
ourselves. Neither can we set a limit to it, for wherever we fix a limit,
space is springing up beyond. Neither can we conceive a smallest or
indivisible portion of it; for within the smallest there is a smaller
still; and even these inconceivable qualities of space, whether the
infinite or the infinitesimal, may be made the subject of reasoning and
have a certain truth to us.

Whether space exists in the mind or out of it, is a question which has no
meaning. We should rather say that without it the mind is incapable of
conceiving the body, and therefore of conceiving itself. The mind may be
indeed imagined to contain the body, in the same way that Aristotle (partly
following Plato) supposes God to be the outer heaven or circle of the
universe. But how can the individual mind carry about the universe of
space packed up within, or how can separate minds have either a universe of
their own or a common universe? In such conceptions there seems to be a
confusion of the individual and the universal. To say that we can only
have a true idea of ourselves when we deny the reality of that by which we
have any idea of ourselves is an absurdity. The earth which is our
habitation and 'the starry heaven above' and we ourselves are equally an
illusion, if space is only a quality or condition of our minds.

Again, we may compare the truths of space with other truths derived from
experience, which seem to have a necessity to us in proportion to the
frequency of their recurrence or the truth of the consequences which may be
inferred from them. We are thus led to remark that the necessity in our
ideas of space on which much stress has been laid, differs in a slight
degree only from the necessity which appears to belong to other of our
ideas, e.g. weight, motion, and the like. And there is another way in
which this necessity may be explained. We have been taught it, and the