I will not here take this expression in the significance that, contrary to the usage' of mathematics, to whom it nevertheless properly belongs, some recent philosophical write have used it, namely that postulation means the same as putting a proposition forth as immedi ately certain without justification or proof; for if we were to allow that synthetic propositions, no matter how evident they might be, could claim unconditional acceptance without any deduction, merely on their own claim, then all critique of the understanding would be lost, and, since there is no lack of audacious pretensions that common belief does not refuse (which is, however,