This divergence between philosophic and physical or mathematical procedure is the point upon which empiricism and mathematicism rely; but these, inferior here to Aristotle, deny the science of absolute being (περὶ ὅντος άπλῶς) and leave in existence only the second order of sciences, which deal with the particular and abstract. There is another important distinction in Aristotle, but to tell the truth it is impossible to say how far he connected it with the preceding distinction between philosophy and physics, with which it is substantially one. Aristotle knew two forms of universal: the universal of the _always_ (τοῡ ἀεί) and that of the _for the most part_ (τοῡ ὡς ἐπὶ τὸ πολύ).[7] He was well aware of the difference between the first, which is truly universal, and the second, which is so only in an approximate and improper manner; and he even asked himself if the _for the most part_ alone existed and not also the _always_; but his interest was directed not so much to the comparative differences of the two series, as to the common character of universality which both of them asserted as against the individual and accidental. Science (he said) is occupied, not with the accidental, but with the universal, whether it be eternal and necessary (ἀναγκαῖον) or only approximately universal (ἐπὶ τὸ πολύ).[8] Philosophy, physics and mathematics felt at this period that they had a common enemy in sensationalism and sophism, and they formed an alliance against this common enemy, rather than as happened later, dissipate their energies in intestinal welfare. [Sidenote: _Controversies concerning Logic in the Middle Ages._] Without dwelling upon the later scepticism, mysticism and mythologism, which represented the dissolution of ancient philosophy and the germ of a new life (especially in Christian mythologism, which had absorbed elements of ancient philosophy and was accompanied by a very developed theology), we must pass on to note the progress which the logical problem made in the schools of the Middle Ages. To look upon mediæval philosophy (as many do) as a negligible episode, a mere detritus of ancient culture quite unconnected with the later spiritual activity, is now no longer possible. Certainly in the disputes of the nominalists and realists, the problem of transcendence and of immanence was neglected. It could not be solved on the presumptions of a philosophy which had at its side a theology, of which it constituted itself the handmaiden. The Platonic transcendence was incurable in Christianity, and those who even to-day seek to purify Christianity from survivals of Greek thought, do not perceive that, in this purification effected by their philosophies of action and of immanence, they are destroying Christianity itself.[9] [Sidenote: _Nominalism and realism._]