of our minds, how is
it that we can picture to ourselves the non-existence of the mind which
is the whole, but not the non-existence of space which, according to the
hypothesis, is the part? For this fact, which we commonly call the
objectivity of space, Kant's theory does not account. In fact Kant
appears to have no escape from assigning this objectivity of space to
delusion. But a theory which requires us to call an ineradicable
conviction of consciousness a delusion cannot be said to explain all the
facts. John Stuart Mill maintains that the other fact, namely, the
conviction of the necessity of mathematical truth, is a delusion. And
his account also must be pronounced for that reason to fail in
accounting for all the facts.

But our present concern is not with Mathematics but with Physics. And
here Kant fails altogether to convince; for, taking Time and the
Perceptive Powers of the Understanding as parts of the human mind, he
shows, what indeed is clearer and clearer every day, that the principles
(so called) of Physics are indispensable Postulates, not indeed of
observing with the senses, but of comprehending with the understanding,
whatever happens. In order to give anything that can be called an
explanation of any event we must show that it falls under the general
rules which constitute the uniformity of Nature. We have no other
meaning for the words understanding or explaining an event. Thinking,
when analysed, is found to consist in bringing all that happens under
universal laws, and no phenomenon can be said to be explained in thought
except by being so related to all other phenomena. But it does not by
any means follow that events cannot happen or cannot affect our senses
without being susceptible of such explanation. To say that an event
cannot be understood, and to say either that it cannot happen or that it
cannot be observed by the senses, are two very different things. The
fact is that Mathematics and Physics do not, as Kant assumes, present
the same problem for solution, and do not therefore admit of one
solution applicable to both. It is not the case that there is a science
of abstract Physics corresponding to the science of Mathematics and
sharing in the same character of necessity. In Mathematics we have
truths which we cannot but accept, and accept as universal and
necessary: in Physics we have no such truths, nor has Kant even
endeavoured to prove that we have. The very question therefore that we