He first of all asked himself what the true value is of our knowledge and
what knowledge is. We believe generally that it is the things which give us
the knowledge that we have of them. But, rather, is it not we who impose on
things the forms of our mind and is not the knowledge that we believe we
have of things only the knowledge which we take of the laws of our mind by
applying it to things? This is what is most probable. We perceive the
things by moulds, so to speak, which are in ourselves and which give them
their shapes and they would be shapeless and chaotic were it
otherwise. Consequently, it is necessary to distinguish the matter and the
form of our knowledge: the matter of the knowledge is the things
themselves. The form of our knowledge is ourselves: "Our experimental
knowledge is a compound of what we receive from impressions and of what our
individual faculty of knowing draws from itself on the occasion of these
impressions."

SENSIBILITY; UNDERSTANDING; REASON.--Those who believe that all we
think proceeds from the senses are therefore wrong; so too are those wrong
who believe that all we think proceeds from ourselves. To say, Matter is an
appearance, and to say, Ideas are appearances, are equally false doctrines.
Now we know by sensibility, by understanding, and by reason. By sensibility
we receive the impression of phenomena; by the understanding we impose on
these impressions their forms, and link them up together; by reason we give
ourselves general ideas of things--universal ones, going beyond or
believing they go beyond the data, even when linked up and systematized.

Let us analyse sensibility, understanding, and reason. Sensibility already
has the forms it imposes on things. These forms are time and space. Time
and space are not given us by matter like colour, smell, taste, or sound;
they are not perceived by the senses; they are therefore the forms of our