d think, be many truths in
physiology (for example) which are only known by a similar indirect
process; and Mr Spencer would hardly detach these from the body of the
science, and call them abstract and the remainder concrete.

[3] Systeme de Politique Positive, ii. 36.

[4] The strongest case which Mr Spencer produces of a scientifically
ascertained law, which, though belonging to a later science, was
necessary to the scientific formation of one occupying an earlier place
in M. Comte's series, is the law of the accelerating force of gravity;
which M. Comte places in Physics, but without which the Newtonian theory
of the celestial motions could not have been discovered, nor could even
now be proved. This fact, as is judiciously remarked by M. Littre, is
not valid against the plan of M. Comte's classification, but discloses a
slight error in the detail. M. Comte should not have placed the laws of
terrestrial gravity under Physics. They are part of the general theory
of gravitation, and belong to astronomy. Mr Spencer has hit one of the
weak points in M. Comte's scientific scale; weak however only because
left unguarded. Astronomy, the second of M. Comte's abstract sciences,
answers to his own definition of a concrete science. M. Comte however
was only wrong in overlooking a distinction. There _is_ an abstract
science of astronomy, namely, the theory of gravitation, which would
equally agree with and explain the facts of a totally different solar
system from the one of which our earth forms a part. The actual facts of
our own system, the dimensions, distances, velocities, temperatures,
physical constitution, &c., of the sun, earth, and planets, are properly
the subject of a concrete science, similar to natural history; but the
concrete is more inseparably united to the abstract science than in any
other case, since the few celestial facts really accessible to us are
nearly all 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.

[5] 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 un