concept must be added to
the perception (in the above case, the concept of cause), under which the
perception is subsumed. The category determines the perceptions in view of
the form of the judgment, gives to the judgment its reference to an object,
and thus gives to the percepts, or rather, concepts (sunshine and warmth),
necessary and universally valid connection. The "reason why the judgments
of others" must "agree with mine" is "the unity of the object to which they
all relate, with which they agree, and hence must also all agree with one
another."

Though the categories take their origin in the nature of the subject, they
are objective and valid for objects of experience, because experience is
possible alone through them. They are not the product, but the ground
of experience. The second difficulty concerns their applicability to
phenomena, which are wholly disparate. By what means is the gulf between
the categories, which are concepts and _a priori_, and perceptions, which
are intuitous and empirical, bridged over? The connecting link is supplied
by the imagination, as the faculty which mediates between sensibility and
understanding to provide a concept with its image, and consists in the
intuition of time, which, in common with the categories, has an _a priori_
character, and, in common with perceptions, an intuitive character, so that
it is at once pure and sensuous. The subsumption of phenomena or empirical
intuitions under the category is effected through the _Schemata_[1] of the
concepts of the understanding, _i.e._, through _a priori_ determinations
of time according to rules, which relate to time-_series_, time-_content_,
time-_order_, and time-_comprehension_, and indicate whether I have to
apply this or that category to a given object.

[Footnote 1: The schema is not an empirical image, but stands midway
between this (the particular intuition of a definite triangle or dog) and
the unintuitable concept, as a general intuition (of a triangle or a dog
in general, which holds alike for right- and oblique-angled triangles, for
poodles and pugs), or as a rule for determining our intuition in accordance
with a concept.]

Each category has its own schema. The schema of quantity is number, as
comprehending the successive addition of homogeneous parts. Filled time
(being in time) is the schema of reality, empty time (not-being in time)
the schema of negation, and more or less filled time (the intensity of
sensati