This same kind of hypothesis supplies us with the reasons why a given sensory current may be, according to circumstances, either conscious or unconscious. The consciousness resulting from the analysis of the molecular wave is, as it were, a supplementary work which may be subsequently added to the realised wave. The propagation of the wave is the essential fact--there is always time to become conscious of it afterwards. It is thus that we happen, in moments of abstraction, to remain insensible to certain even very powerful excitements. Our nervous system registers them, nevertheless, and we can find them again, later on, within the memory. This is the effect of a belated analysis. The converse phenomenon occurs much more frequently. We remark many actions and perceptions which occur the first time with consciousness, emotion, and effort. Then, when they are repeated, as coordination becomes stronger and easier, the reflex consciousness of the operation becomes feebler. This is the law of habit, which slowly carries us towards automatism. These observations have even been extended, and the endeavour made to apply them to the explanation of the origin of reflex actions and of instincts which have all started with consciousness. This is a rather bold attempt, for it meets with many serious difficulties in execution; but the idea seems fairly correct, and is acceptable if we may limit it. It is certain that the consciousness accompanies the effort towards the untried, and perishes as soon as it is realised. Whence comes this singular dilemma propounded to it by nature: to create something new or perish? It really seems that my hypothesis explains this. Every new act is produced by nerve currents, which contain many of those variable elements which the consciousness perceives; but, in proportion as the action of the brain repeats itself and becomes more precise and more exact, this variable element becomes attenuated, falls to its lowest pitch, and may even disappear in the fixation of habit and instinct. My hypothesis much resembles the system of parallelism. It perfects it, as it seems to me, as much as the latter has perfected materialism. We indeed admit a kind of parallelism between the consciousness and the object of cognition; but these two series are not independent, not simply placed in juxtaposition as is possible in ordinary parallelism; they are united and fused together so as to complete each other. This new theory appears to me to represent a better form of the series of attempts which have been inspired by the common necessity of making the phenomena of consciousness accord with the determinism of physical facts.