angle is subtended by the greater side, or that every event has a
definite cause among earlier events, though I cannot examine all
triangles or all events one by one. This is because the postulates of
geometry and the law of causality are types of order which my mind
_puts_ into the data of its knowledge in the very act of attending to
them, and it is therefore certain that I shall never perceive or think
anything which does not conform to these types.

I give Kant's answer to the problem of Criticism not because I believe
it to be the correct one, but to show what important consequences follow
from our acceptance of a solution of this problem. If it is true that
one of the constituent elements of every piece of knowledge is a lump of
crude sensation, it follows that we can have no knowledge about our own
minds or souls, and still less about God, since, if there are such
beings as my soul and God, at any rate neither furnishes me with
sense-data. Hence a great part of Kant's famous _Critique of Pure
Reason_ is taken up by an elaborate attempt to show that psychology and
theology contain no real knowledge. We cannot even know whether there is
any probability for or against the existence of the soul or of God,
though Kant was very anxious to show that it is our duty on moral
grounds to _believe_ very firmly in both. Now if Kant is right about
this, his result is tremendously important. If psychology and theology
are wholly devoid of scientific value, it is most desirable that we
should know this, not only that we may not waste time in studying them,
but because it may reasonably make a very great difference to the
practical ordering of our lives. If Kant can be proved wrong, it is
equally important to be convinced that he is wrong. We may have been led
by belief in his teaching to neglect the acquisition of a great deal of
knowledge of high intrinsic interest, and may even have been betrayed
into basing the conduct of life on wrong principles. If, for example, we