It is therefore from the human point of view only that we can speak of
space, extended objects, etc. If we depart from the subjective
condition, under which alone we can obtain external intuition, or, in
other words, by means of which we are affected by objects, the
representation of space has no meaning whatsoever. This predicate is
only applicable to things in so far as they appear to us, that is, are
objects of sensibility. The constant form of this receptivity, which we
call sensibility, is a necessary condition of all relations in which
objects can be intuited as existing without us, and when abstraction of
these objects is made, is a pure intuition, to which we give the name
of space. It is clear that we cannot make the special conditions of
sensibility into conditions of the possibility of things, but only of
the possibility of their existence as far as they are phenomena. And so
we may correctly say that space contains all which can appear to us
externally, but not all things considered as things in themselves, be
they intuited or not, or by whatsoever subject one will. As to the
intuitions of other thinking beings, we cannot judge whether they are
or are not bound by the same conditions which limit our own intuition,
and which for us are universally valid. If we join the limitation of a
judgement to the conception of the subject, then the judgement will
possess unconditioned validity. For example, the proposition, “All
objects are beside each other in space,” is valid only under the
limitation that these things are taken as objects of our sensuous
intuition. But if I join the condition to the conception and say, “All
things, as external phenomena, are beside each other in space,” then
the rule is valid universally, and without any limitation. Our
expositions, consequently, teach the reality (i.e., the objective
validity) of space in regard of all which can be presented to us
externally as object, and at the same time also the ideality of space
in regard to objects when they are considered by means of reason as
things in themselves, that is, without reference to the constitution of
our sensibility. We maintain, therefore, the empirical reality of space
in regard to all possible external experience, although we must admit
its transcendental ideality; in other words, that it is nothing, so
soon as we withdraw the condition upon which the possibility of all
experience depends and look upon space as something that belongs to
things in themselves.