This relation of contraries to the higher conception which logically must include them is one of the well-worn problems of the higher metaphysics. The proper explanation would seem to be, as suggested above, that the synthesis of contraries is capable of formal expression only, but not of interpretation. In pursuing the search for their union we pass into a realm of thought not unlike that of the mathematician when he deals with hypothetical quantities, those which can only be expressed in symbols--, √1 for example,--but uses them to good purpose in reaching real results. The law does not fail, but its operations can no longer be expressed under material images. They are symbolic and for speculative thought alone, though pregnant with practical applications. As I have hinted, in all real contraries it is theoretically possible to accept either the one or the other. As in mathematics, all motion can be expressed either under formulas of initial motion (mechanics), or of continuous motion (kinematics), or as all force can be expressed as either static or as dynamic force; in either case the other form assuming a merely hypothetical or negative position; so the logic of quality is competent to represent all existence as ideal or as material, all truth as absolute or all as relative, or even to express the universe in formulæ of being or of not-being. This perhaps was what Heraclitus meant when he propounded his dark saying: “All things are _and_ are not.” He added that “All is not,” is truer than “All is.” Previous to his day, Buddha Sakyamuni had said: “He who has risen to the perception of the not-Being, to the Unconditioned, the Universal, his path is difficult to understand, like the flight of birds in the air.”[37-1] Perhaps even he learned his lore from some older song of the Veda, one of which ends, “Thus have the sages, meditating in their souls, explained away the fetters of being by the not-being.”[37-2] The not-being, as alone free from space and time, impressed these sages as the more real of the two, the only absolute. The error of assigning to the one universal a preponderance over the other arose from the easy confusion of pure with applied thought. The synthesis of contraries exists in the formal law alone, and this is difficult to keep before the mind. In concrete displays they are forever incommensurate. One seems to exclude the other. To see them correctly we must there treat them as alternates. We may be competent, for instance, to explain all phenomena of mind by organic processes; and equally competent to explain all organism as effects of mind; but we must never suppose an immediate identity of the two; this is only to be found in the formal law common to both; still less should we deny the reality of either. Each exhausts the universe; but at every step each presupposes the other; their synthesis is life, a concept hopelessly puzzling unless regarded in all its possible displays as made up of both.