10. ANALYSIS OF CHANGE.—_Change_ (_Mutatio_, _Motus_, μεταβολή, κίνησις) is one of those simplest concepts which cannot be defined. We may describe it, however, as _the transition of a being from one state to another_. If one thing entirely disappeared and another were substituted for it, we should not regard the former as having been changed into the latter. When one thing is put in the place of another, each, no doubt, undergoes a change of place, but neither is changed into the other. So, also, if we were to conceive a thing as absolutely ceasing to exist, as lapsing into nothingness at a given instant, and another as coming into existence out of nothingness at the same instant (and in the same place), we should not consider this double event as constituting a real change of the former thing into the latter. And although our _senses_ cannot testify to anything beyond _sequence_ in sense phenomena, our _reason_ detects in real change something other than a total substitution of things for one another, or continuous total cessations and inceptions of existence in things. No doubt, if we conceive the whole phenomenal or perceptible universe and all the beings which constitute this universe as essentially contingent, and therefore dependent for their reality and their actual existence on a Supreme, Necessary Being who created and conserves them, who at any time may cease to conserve any of them, and produce other and new beings _out of nothingness_, then such absolute cessations and inceptions of existence in the world would not be impossible. God might _annihilate_, _i.e._ cease to conserve in existence, this or that contingent being at any instant, and at any instant _create_ a new contingent being, _i.e._ produce it in its totality from no pre-existing material. But there is no reason to suppose that this is what is constantly taking place in Nature: that all change is simply a series of annihilations and creations. On the contrary, the modes of being which appear and disappear in real change, in the transition of anything from one state to a really different state of being, do not appear _de novo_, _ex nihilo_, as absolute beginnings out of nothingness; or disappear _totaliter_, _in nihilum_, as absolute endings or lapses of reality into nothingness. The real changes which take place in Nature are due to the operation of natural causes. These causes, being finite in their operative powers, cannot create, _i.e._ produce new being from nothingness. They can, however, with the concurrence of the Omnipotent Being, modify existing modes of being, _i.e._ make actual what was only potential in these latter. The notion of change is not verified in the conception of successive annihilations and creations; for there is involved in the former concept not merely the notion of a real difference between the two _actual_ states, that before and that after the change, but also the notion of some _potential_ reality persisting throughout the change,