If all C is D, then all A is B.
But, all C is D.
Therefore, all A is B.
Explain the difference between (1) the unity of the understanding which allows the concept A to be brought under the concept B and (2) the unity of reason which allows the judgment All A is B to be explained by the principle, If all C is D, then all A is B. In particular: both (1) and (2) involve the unification of the same manifold of possible cognitions: which ones? In virtue of what, and for what purpose, are they united in (2), as opposed to in (1)?