Auguste Comte and Positivism
required for discovering and proving the law of gravitation as an universal property of bodies, and
have therefore an indispensable place in the abstract science as its fundamental data.
 The only point at which the general principle of the series fails in its application, is the
subdivision of Physics; and there, as the subordination of the different branches scarcely exists,
their order is of little consequence. Thermology, indeed, is altogether an exception to the
principle of decreasing generality, heat, as Mr Spencer truly says being as universal as
gravitation. But the place of Thermology is marked out, within certain narrow limits, by the ends
of the classification, though not by its principle. The desideratum is, that every science should
precede those which cannot be scientifically constitute or rationally studied until it is known. It is
as a means to this end, that the arrangement of the phaenomena in the order of their dependence
on one another is important. Now, though heat is as universal a phaenomenon as any which
external nature presents, its laws do not affect, in any manner important to us, the phaenomena of
Astronomy, and operate in the other branches of Physics only as slight modifying agencies, the
consideration of which may be postponed to a rather advanced stage. But the phaenomena of
Chemistry and Biology depend on them often for their very existence. The ends of the
classification require therefore that Thermology should precede Chemistry and Biology, but do
not demand that it should be thrown farther back. On the other hand, those same ends, in another
point of view, require that it should be subsequent to Astronomy, for reasons not of doctrine but
of method: Astronomy being the best school of the true art of interpreting Nature, by which
Thermology profits like other sciences, but which it was ill adapted to originate.
 The philosophy of the subject is perhaps nowhere so well expressed as in the "Systeme de
Politique Positive" (iii. 41). "Concu logiquement, l'ordre suivant lequel nos principales theories
accomplissent l'evolution fondamentale resulte necessairement de leur dependence mutuelle.
Toutes les sciences peuvent, sans doute, etre ebauchees Ã la fois: leur usage pratique exige
meme cette culture simultanee. Mais elle ne peut concerner que les inductions propres Ã chaque
classe de speculations. Or cet essor inductif ne saurait fournir des principes suffisants qu'envers
les plus simples etudes. Partout ailleurs, ils ne peuvent etre etablis qu'en subordonnant chaque
genre d'inductions scientifiques Ã l'ensemble des deductions emanees des domaines moins
compliques, et des-lors moins dependants. Ainsi nos diverses theories reposent dogmatiquement
les unes sur les autres, suivant un ordre invariable, qui doit regler historiquement leur avenement
decisif, les plus independantes ayant toujours du se developper plus tot."
 "Science," says Mr Spencer in his "Genesis," "while purely inductive is purely qualitative....
All quantitative prevision is reached deductively; induction can achieve only qualitative
prevision." Now, if we remember that the very first accurate quantitative law of physical
phaenomena ever established, the law of the accelerating force of gravity, was discovered and
proved by Galileo partly at least by experiment; that the quantitative laws on which the whole
theory of the celestial motions is grounded, were generalized by Kepler from direct comparison
of observations; that the quantitative law of the condensation of gases by pressure, the law of
Boyle and Mariotte, was arrived at by direct experiment; that the proportional quantities in which
every known substance combines chemically with every other, were ascertained by innumerable
experiments, from which the general law of chemical equivalents, now the ground of the most
exact quantitative previsions, was an inductive generalization; we must conclude that Mr Spencer
has committed himself to a general proposition, which a very slight consideration of truths
perfectly known to him would have shown to be unsustainable.
Again, in the very pamphlet in which Mr Spencer defends himself against the supposition of
being a disciple of M. Comte ("The Classification of the Sciences," p. 37), he speaks of "M.