Herefrom it would appear to follow that only individual perceptions are true, and that all general conceptions without exception must be false. If each notion (λεκτὸν) is incorporeal, and consequently unreal, [272] will not absence of reality in a much higher degree belong to the notion of what is general? [(a) Individual perceptions alone true; yet a higher truth assigned to general conceptions.] Individual notions refer directly to perceptions, i.e. to things incorporeal; nevertheless they indirectly refer to the things perceived, i.e. to what is material. But general notions do not even indirectly refer to anything corporeal; they are pure fabrications of the mind, which have nothing real as their object. This the Stoics explicitly maintained. [273] It was therefore a gross inconsistency to attribute notwithstanding to these general conceptions, to which no real objects correspond, a higher truth and certainty than belongs to the perceptions of individual objects, but an inconsistency which the Stoic system made not the slightest attempt to overcome. [(b) Theory of universal intermingling.] The materialism of the Stoics likewise led to some remarkable assertions in the province of natural science. If the attributes of things, the soul and even the powers of the soul, are all corporeal, the relation of attributes to their objects, of the soul to the body, of one body to another body, is that of mutual intermingling. [274] Moreover, inasmuch as the essential attributes of any definite material belong to every part of that material, and the soul resides in every part of the body, without the soul’s being identical with the body, and without the attributes being identical with the material to which they belong, or with one another; it follows that one body may intermingle with another not only by occupying the vacant spaces in that body, but by interpenetrating all its parts, without, however, being fused into a homogeneous mass with it. [275] This view involves not only a denial of the impenetrability of matter, but it further supposes that a smaller body when mingled with a greater body will extend over the whole of the latter. It is known as the Stoic theory of universal intermingling (κρᾶσις δι’ ὅλων), and is alike different from the ordinary view of mechanical mixture and from that of chemical mixture. It differs from the former in that every part of the one body is interpenetrated by every part of the other; from the latter, because the bodies after mixture still retain their own properties. [276] This peculiar theory, which is one of the much debated but distinctive features of the Stoic system, [277] cannot have been deduced from physical causes. On the contrary, the arguments by which Chrysippus supported it prove that it was ultimately the result of metaphysical considerations. [278] We have, moreover, no reason to doubt it as a fact, inasmuch as the materialistic undercurrent of the Stoic system affords the best explanation of it.