[Sidenote: They should be kept apart too by psychology.] It is now time to add that the relation of inner causality is purely dynamic, and has no analogy with the relation of two external phenomena which condition one another. For as the latter are capable of recurring in a homogeneous space, their relation can be expressed in terms of a law, whereas deep-seated psychic states occur once in consciousness and will never occur again. A careful analysis of the psychological phenomenon led us to this conclusion in the beginning: the study of the notions of causality and duration, viewed in themselves, has merely confirmed it. [Sidenote: Freedom real but indefineable.] We can now formulate our conception of freedom. Freedom is the relation of the concrete self to the act which it performs. This relation is indefinable, just because we _are_ free. For we can analyse a thing, but not a process; we can break up extensity, but not duration. Or, if we persist in analysing it, we unconsciously transform the process into a thing and duration into extensity. By the very fact of breaking up concrete time we set out its moments in homogeneous space; in place of the doing we put the already done; and, as we have begun by, so to speak, stereotyping the activity of the self, we see spontaneity settle down into inertia and freedom into necessity. Thus, any positive definition of freedom will ensure the victory of determinism. Shall we define the free act by saying of this act, when it is once done, that it might have been left undone? But this assertion, as also its opposite, implies the idea of an absolute equivalence between concrete duration and its spatial symbol: and as soon as we admit this equivalence, we are led on, by the very development of the formula which we have just set forth, to the most rigid determinism. Shall we define the free act as "that which could not be foreseen, even when all the conditions were known in advance?" But to conceive all the conditions as given, is, when dealing with concrete duration, to place oneself at the very moment at which the act is being performed. Or else it is admitted that the matter of psychic duration can be pictured symbolically in advance, which amounts, as we said, to treating time as a homogeneous medium, and to reasserting in new words the absolute equivalence of duration with its symbol. A closer study of this second definition of freedom will thus bring us once more to determinism.