erience is certainly surprising. Kant's solution of the
problem, though not valid in my opinion, is interesting. It is, however,
very difficult, and is differently understood by different philosophers.
We can, therefore, only give the merest outline of it, and even that
will be thought misleading by many exponents of Kant's system.

What Kant maintained was that in all our experience there are two
elements to be distinguished, the one due to the object (i.e. to what we
have called the 'physical object'), the other due to our own nature. We
saw, in discussing matter and sense-data, that the physical object is
different from the associated sense-data, and that the sense-data are to
be regarded as resulting from an interaction between the physical
object and ourselves. So far, we are in agreement with Kant. But what
is distinctive of Kant is the way in which he apportions the shares of
ourselves and the physical object respectively. He considers that the
crude material given in sensation--the colour, hardness, etc.--is due
to the object, and that what we supply is the arrangement in space
and time, and all the relations between sense-data which result from
comparison or from considering one as the cause of the other or in any
other way. His chief reason in favour of this view is that we seem
to have _a priori_ knowledge as to space and time and causality and
comparison, but not as to the actual crude material of sensation. We can
be sure, he says, that anything we shall ever experience must show the
characteristics affirmed of it in our _a priori_ knowledge, because
these characteristics are due to our own nature, and therefore
nothing can ever come into our experience without acquiring these
characteristics.

The physical object, which he calls the 'thing in itself',(1) he regards
as essentially unknowable; what can be known is the object as we have it
in experience, which he calls the 'phenomenon'. The phenomenon, being
a joint product of us and the thing in itself, is sure to have those
characteristics which are due to us, and is therefore sure to conform
to our _a priori_ knowledge. Hence this knowledge, though true of all
actual and possible experience, must not be supposed to apply outside
experience. Thus in spite of the existence of _a priori_ knowledge, we
cannot know anything about the thing in itself or about what is not
an actual or possible object of experience. In this way he tries to
reconcile and harmonize