[…] mathematical concepts are definable in terms of logical concepts, mathematical truths are reducible to logical truths, and mathematical knowledge is really logical knowledge. MacFarlane, What does it mean to say that logic is formal?, p.7

A popular way to attack logicism is to argue that the “logic” to which mathematics has been reduced is really just more mathematics. Poincare charges that Russel’s “logical” principles are really intuitive, synthetic judgements in disguise: “We regard them as intuitive when we meet them more or less explicitly enunciated in mathematical treatises; have they changed character because the meaning of the word logic has been enlarged and now we find them in a book entitled ‘Treatise on Logic’”? Quine, a more sympathetic critic, draws a similar conclusion: “Frege, Whitehead and Russell made a point of reducing mathematics to logic; Frege claimed in 1884 to have proved in this way, contrary to Kant, that the truths of arithmetic are analytic. But the logic capable of encompassing this reduction was logic inclusive of set theory.” Applied to the full-fledged logicism that identifies numbers with classes, Quine’s criticism is just - and nearly universally accepted. [Note] Frege’s class existence axiom, a plausible candidate for a logical law, was shown to be inconsistent, and all known consistent theories of classes require existence assumptions that seem to lack the “special character” of logic. For Frege, this spelled the death of logicism. Although Russell persisted in maintaining the logicist theses, he acknowledged that his axioms of infinity and reducibility are not logical and must be taken as hypotheses. MacFarlane, What does it mean to say that logic is formal?, p.8