 This is nowadays called ‘Frege’s  Theorem’.[33]  Frege’s Theorem has Principle (A) as its hypothesis. Curiously, the stress Frege places, in the Grundlagen, on the importance of this principle (that two concepts have the same number just in case they are gleichzahlig) is dissipated in the Grundgesetze, where the two halves of the biconditional appear widely separated: in §53 Frege proves that if two concepts correspond 1–1, then their numbers are identical, and in §69 he proves the converse. But nowhere in the Grundgesetze does he re-assemble the biconditional and accord it prime philosophical importance. Had he done so, he might well have become the first neo-Fregean in response to Russell’s Paradox. In order to do so, however, he would have had to overcome his reluctance to view (A) as a logical  axiom.[34] 