Many other concepts might be added to the preceding, among them, those of the moral sciences. I forbear, because the history of their fluctuations would in itself exact a volume. Till now, these have been ill-determined, badly defined. May we even speak of any regular evolution? Have they not rather suffered _corsi e ricorsi_, which bring them back perennially to their point of departure? Whenever—during a development of centuries—the work of abstraction has succeeded, we have seen it pass through successive phases:—generic ideas, intermediate forms, higher forms—but not by any constant process. Sometimes it has rapidly attained the period of complete simplification, as in mathematics; sometimes it is long arrested in its progress, as in the natural sciences: sometimes, again, as in the less established sciences, it is incapable even to the present day of transcending the lowest stages. CHAPTER VI. CONCLUSION. We have endeavored to show how the faculty of abstracting and of generalising has been developed empirically, and to follow it in its spontaneous and natural evolution as shown in history,—not in the philosophical speculations which are only its efflorescence, and which, for the most part, ignore or despise its origins. It remains to us, in conclusion, to seek out how, and by what causes, this intellectual process has constituted and developed itself: further—what are the different directions it has followed in the course of its development. I. To contemporary psychology, the mind is a sum of processes of dissimilar nature, whose mode of appearance and of evolution depends upon predetermined conditions. In the total of intellectual operations, abstraction is a process of secondary formation: it does not belong to the primary stratum of sensations and percepts, of appetites and tendencies, of primitive emotions. We found however that it was there in embryo. How then, instead of remaining in this rudimentary state, has it been so differentiated as to become a function proper to the intellect, and with a long development that is still in progress? The primary condition is the existence of _attention_, which brings a few points into relief, amid the general confusion. We have shown elsewhere that attention itself depends originally upon the instinct of individual preservation.[136] Attention, however, can only precede and prepare for abstraction, because it is a momentary state of application to the variable aspects of events, and does not isolate anything. We know how the first labor of separation, of dissociation, takes effect in the formation of generic images, and how the extracted quality _fixed_ itself, for better or worse, by the aid of a visual, auditory, tactile scheme, by a movement, a gesture, which confers on it a sort of independence.