32 THOMAS WHITTAKER : it, we can explicitly state an axiom or postulate which cer- tainly is not devoid of meaning : namely, that there is a whole of Mind and that that whole is perdurable. This seems, both in itself and from scientific analogy, the most reasonable position. It is already laid down in Plato's Phado, though in a form which, through its close union with direct examination of the arguments for the permanence of the in- dividual soul, has given critics trouble to disentangle. Thus it is, historically, nearly as old as the axiom of the physical perdurability of Matter. The Conservation of Energy, with its apparently intermediate position between physics and metaphysics, was naturally much later to receive satisfactory statement. Appearing for long in the guise of propositions about the ambiguous entity called "force," with its sugges- gestion at once of inherence in matter and of subjective activity, it had to be denned as an altogether phenomenal truth, and thrown over to the objective side, before scientific clearness could be attained. Given the perdurability of Mind, as distinguished at once from the merely formal axiom of Identity, that A is A, and from the axioms, having reference to the object-world, that Matter and Energy persist in time, we can now state intelligibly the further questions : Are in- dividual minds or souls alternately segregated from the whole of Mind and re-absorbed into it ; there being thus emergence and cessation of ever new intrinsic differences ? Or do they represent permanent distinctions, through changes of phenom- enal manifestation, within a total intellectual system ? To state the questions is not of course to answer them ; but, once the general axiom of perdurability is admitted, they become accessible to the laws of thought. The criterion seems to be, Which supposition is most thinkable in ac- cordance with the nature of mind? To return now to a topic just raised under the head of Psychology. The amended classification of the sciences here proposed seems to exclude Practical and Esthetic Philosophy. Yet these too have a scientific or speculative aspect, as on the other hand Metaphysics and Logic, which are included, may be treated not only as speculative sciences but as disciplines regulative of thought. Again, no place has been found in the diagram for the concrete and applied sciences. The answer to these objections is that any arrange- ment in space must necessarily be inadequate to the true order of the sciences, both positive and philosophical ; since all of them together have their existence in mind or the unextended. A diagram can only serve as an aid to mental conception ; it does not directly show forth the real order.
