To convince ourselves that they are both real, very little reflection is needed. We have actual experience of both those elements of reality in our consciousness and memory of our own selves. Every human individual in the enjoyment of his mental faculties knows himself as an abiding, self-identical being, yet as constantly undergoing real changes; so that throughout his life he is really the same being, though just as certainly he really changes. In external nature, too, we observe on the one hand innumerable processes of growth and decay, of motion and interaction; and on the other hand a similarly all-pervading element of sameness or identity amid all this never-ending change. 7. THE POTENTIAL AND THE ACTUAL. (_a_) POSSIBILITY, ABSOLUTE, RELATIVE, AND ADEQUATE.—It is from our experience of actuality and change that we derive not only our notion of temporal duration, but also our notion of _potential being_ or _possibility_, as distinct from that of _actual being_ or _actuality_. It is from our experience of what actually exists that we are able to determine what can, and what cannot exist. We know from experience what gold is, and what a tower is; and that it is intrinsically possible for a golden tower to exist, that such an object of thought involves no contradiction, that therefore its existence is not impossible, even though it may never actually exist as a fact. Similarly, we know from experience what a square is, and what a circle is; and that it is intrinsically impossible for a square circle to exist, that such an object of thought involves a contradiction, that therefore not only is such an object never actually existent in fact, but that it is in no sense real, in no way possible. Thus, _intrinsic_ (or _objective_, _absolute_, _logical_, _metaphysical_) possibility is the mere non-repugnance of an object of thought to actual existence. Any being or object of thought that is conceivable in this way, that can be conceived as capable of actually existing, is called intrinsically (or objectively, absolutely, logically, metaphysically) possible being. The absence of such intrinsic capability of actual existence gives us the notion of the intrinsically (objectively, absolutely, logically, metaphysically) impossible. We shall return to these notions again. They are necessary here for the understanding of real change in the actual universe.