antecedent which is confounded with the sum of its concomitants, as when an explosion is said to be the effect of a spark. Of course we are speaking of causation as exercised under the conditions of time, space, matter, and motion. It is then identical with the transmission of energy and obeys the laws of energy. And to talk about causation under any other conditions than these is utter nonsense. But Plotinus and other philosophers exclude the most essential of the conditions specified from their enquiries into the ultimate origin of things. We are expressly informed that the genesis of Nous from the One, and of Soul from Nous, must not be conceived as taking place in time but in eternity.[472] Unfortunately those who make such reservations are not consistent. They continue to talk about power, causation, priority, and so forth, as if these conceptions were separable from time. Hence they have to choose between making statements which are absolutely unintelligible and making statements which are absolutely untrue. Perhaps the processes of logic and mathematics may be adduced as an exception. It may be contended that the genus is prior to the species, the premise to the conclusion, the unit to the multiple, the line to the figure, in reason though not in time. And Plotinus avails himself to the fullest extent of mathematical and logical analogies in his transcendental constructions. His One is the starting-point of numeration, the centre of a circle, the identity involved in difference; and under each relation it claims an absolute priority, of which causal power is only the most general expression. We have already seen how a multitude of archetypal Ideas spring from the supreme Nous as from their fountain-head. Their production is explained, on the lines of Plato’s _Sophist_, as a process of dialectical derivation. By logically analysing the conception of self-consciousness, we obtain, first of all, Nous itself, or Reason, as the subject, and Existence as the object of thought. Subject and object, considered as the same with one another, give us Identity; considered as distinct, they give us Difference. The passage from one to the other gives Motion; the limitation of thought to itself gives Rest. The plurality of determinations so obtained gives number and quantity, their specific difference gives quality, and from these principles everything else is derived.[473] It might seem as if, here at least, we had something which could be called a process of eternal generation—a causal order independent of time. But, in reality, the assumed sequence exists only in our minds, and there it takes place under the form of time, not less inevitably than do the external re-arrangements of matter and motion. Thus in logic and mathematics, such terms as priority, antecedence, and evolution can only be used to signify the order in which our knowledge is acquired; they do not answer to causal relations existing among things in themselves.