Those who deny the possibility of all non-empirical knowledge naturally hold that every axiom is ultimately based on observation.
But, in so doing, it accepted the particularism of experience and proceeded to supplement it from non-empirical sources.
Both thesis and antithesis may be true, the latter of the world of sense and the former of its non-empirical ground.
The proofs which Kant offers of them are, indeed, of a non-empirical a priori character.
empirical em·pir·i·cal (ěm-pēr'ĭ-kəl)
Relying on or derived from observation or experiment.
Verifiable or provable by means of observation or experiment.
Of or being a philosophy of medicine emphasizing practical experience and observation over scientific theory.