[128] Sigwart in his Logik, Book II. (English translation by Helen Dendy) has made a profound study of the classification of the psychological laws in psychology, and their relative value. He divides them into three categories, according to the nature of the relations which they express: 1. Psychophysical laws which formulate constant relations between states of consciousness and the cerebral states. Ex. the relation between the sensation directly received, and the image that is reproduced in consciousness. 2. Psychological laws properly so-called; these express the internal relations of the states of consciousness. Ex. Law of conservation of impressions, law of association, law of systematisation by volition. 3. Laws expressive of the reciprocal action that human thoughts and volitions exert one upon the other: they presuppose the intervention of social causes, and are to this day vague and ill-determined; hence there are no fixed rules for the government of humanity, or the bringing up of children.
[129] “Fundamental laws are, or should be, only the simplest, most abridged, and most economical mode of expressing facts, within the limits of precision possible to our observations and experiences. The laws of nature are simple, essentially because—among all the possible modes of expression—we choose the simplest” (see Mach, Mechanics, Chicago, 1893, and Popular Scientific Lectures, 23d ed., Chicago, 1898, under the headings “Economy of Thought,” “Law,” etc.). “In formulating a general, simple, precise law, based upon relatively few experiences, which, moreover, present certain divergencies, we only obey a necessity from which the human mind cannot free itself.” (Poincaré.)
[130] Since our subject is the tracing out of the concept of law in its different degrees, starting from the generic image, we have no need to study the nature of the laws proper to each science (logic, mathematics, mechanics, physico-chemistry, biology, etc.), nor to discuss their value. For this point, see Boutroux, L’idée de loi naturelle dans la science et la philosophie contemporaine. Paris, 1895.
[131] Brown, quoted by Quatrefages (Précurseurs de Darwin, p. 218), who adds, “If this were the case, one would not find many species denoted by particular names among savages, and our own illiterate population. The general notion of species is on the contrary one of those that are forced upon us, directly we look round. The difficulty is to formulate it clearly, to give it scientific precision, and this is a very real problem.”
[132] Quatrefages (op. cit., pp. 219-222) gives a great number of definitions of species. A few may be quoted: “Species should be defined as a succession of wholly similar individuals, perpetuated by means of generation” (De Jussieu).—“Species is a constant succession of like individuals, which reproduce themselves” (Buffon).—“By species we mean any collection of similar individuals, that have been produced by individuals like unto themselves” (Lamarck).—“Species is the individual repeated and continued in time and space” (Blainville).—“Species is the totality of all individuals that have the same origin, and of those that are as like them, as they are among themselves” (Brown), etc., etc.
[133] For the transformists, as is well known, variety, race, and species are not fixed concepts. “From variety to race, from race to species, there is a continuous insensible passage. Individual modifications, at first slight, give rise to a variety or to a race. Continuing to augment, and extending to a constantly increasing number of individuals, they may come to constitute specific characters. Pursuing its evolution, the species then finally reaches the rank of the genus, family, etc.”
[134] De l’Espèce, Ch. II., §§ 6 and 7.
[135] Nouveaux Essais, III, § 6, 23.
[136] Psychology of Attention, Ch. I. (Chicago: Open Court Publishing Co.)
[137] For a study of the function and practical value of symbolism consult Ferrero, Les lois psychologiques du symbolisme; Paris, F. Alcan.