exception to this or that rule. If, on the other hand, a judgement
carries with it strict and absolute universality, that is, admits of
no possible exception, it is not derived from experience, but is valid
absolutely a priori.

Empirical universality is, therefore, only an arbitrary extension of
validity, from that which may be predicated of a proposition valid
in most cases, to that which is asserted of a proposition which
holds good in all; as, for example, in the affirmation, "All bodies
are heavy." When, on the contrary, strict universality characterizes
a judgement, it necessarily indicates another peculiar source of
knowledge, namely, a faculty of cognition a priori. Necessity and
strict universality, therefore, are infallible tests for
distinguishing pure from empirical knowledge, and are inseparably
connected with each other. But as in the use of these criteria the
empirical limitation is sometimes more easily detected than the
contingency of the judgement, or the unlimited universality which we
attach to a judgement is often a more convincing proof than its
necessity, it may be advisable to use the criteria separately, each
being by itself infallible.

Now, that in the sphere of human cognition we have judgements
which are necessary, and in the strictest sense universal,
consequently pure a priori, it will be an easy matter to show. If we
desire an example from the sciences, we need only take any proposition
in mathematics. If we cast our eyes upon the commonest operations of
the understanding, the proposition, "Every change must have a
cause," will amply serve our purpose. In the latter case, indeed,
the conception of a cause so plainly involves the conception of a
necessity of connection with an effect, and of a strict universality