[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 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.

[6] The philosophy of the subject is perhaps nowhere so well expressed
as in the "Système de Politique Positive" (iii. 41). "Conçu logiquement,
l'ordre suivant lequel nos principales théories accomplissent