of causation! And education,
the whole secret of which consists in proceeding from the easy to the
difficult, the concrete to the abstract, ought to be turned the other
way, and pass from the abstract to the concrete.

M. Comte puts a second argument in favour of his hierarchy of the
sciences thus:--

"Un second caractere tres-essentiel de notre classification, c'est
d'etre necessairement conforme a l'ordre effectif du developpement
de la philosophie naturelle. C'est ce que verifie tout ce qu'on
sait de l'histoire des sciences."[25]

But Mr. Spencer has so thoroughly and completely demonstrated the
absence of any correspondence between the historical development of the
sciences, and their position in the Comtean hierarchy, in his essay on
the "Genesis of Science," that I shall not waste time in repeating his
refutation.

A third proposition in support of the Comtean classification of the
sciences stands as follows:--

"En troisieme lieu cette classification presente la propriete
tres-remarquable de marquer exactement la perfection relative des
differentes sciences, laquelle consiste essentiellement dans le
degre de precision des connaissances et dans leur co-ordination
plus ou moins intime."[26]

I am quite unable to understand the distinction which M. Comte
endeavours to draw in this passage in spite of his amplifications
further on. Every science must consist of precise knowledge, and that
knowledge must be co-ordinated into general proportions, or it is not
science. When M. Comte, in exemplification of the statement I have
cited, says that "les phenomenes organiques ne comportent qu'une etude a
la fois moins exacte et moins systematique que les phenomenes des corps
bruts," I am at a loss to comprehend what he means. If I affirm that
"when a motor nerve is irritated, the muscle connected with it becomes
simultaneously shorter and thicker, without changing its volume," it
appears to me that the statement is as precise or exact (and not merely
as true) as that of the physicist who should say, that "when a piece of
iron is heated, it becomes simultaneously longer and thicker and
increases in volume;" nor can I discover any difference, in point of
precision, between the statement of the morphological law that "animals
which suckle their young have two occipital condyles," and the
enunciation of the physical law that "water subjected to electrolysis
is replaced by an eq