Such a dialectical doctrine will relate not to the unity of understanding in concepts of experience, but to the unity of reason in mere ideas, whose conditions, since, as a synthesis according to rules, must first be congruent with the understanding, and yet at the same time, as the ab solute unity of this synthesis, must be congruent with reason, will be too large for the understanding if this unity is to be adequate to the unity of reason, and yet too small for reason if they are suited to the under standing; from this there must arise a contradiction that cannot be avoided no matter how one may try.