Acoustics, Optics, and Electrology. These he attempts to arrange on the
same principle of increasing speciality and complexity, but they hardly
admit of such a scale, and M. Comte's mode of placing them varied at
different periods. All the five being essentially independent of one
another, he attached little importance to their order, except that
barology ought to come first, as the connecting link with astronomy, and
electrology last, as the transition to chemistry.

If the best classification is that which is grounded on the properties
most important for our purposes, this classification will stand the
test. By placing the sciences in the order of the complexity of their
subject matter, it presents them in the order of their difficulty. Each
science proposes to itself a more arduous inquiry than those which
precede it in the series; it is therefore likely to be susceptible, even
finally, of a less degree of perfection, and will certainly arrive later
at the degree attainable by it. In addition to this, each science, to
establish its own truths, needs those of all the sciences anterior to
it. The only means, for example, by which the physiological laws of life
could have been ascertained, was by distinguishing, among the
multifarious and complicated facts of life, the portion which physical
and chemical laws cannot account for. Only by thus isolating the effects
of the peculiar organic laws, did it become possible to discover what
these are. It follows that the order in which the sciences succeed one
another in the series, cannot but be, in the main, the historical order
of their development; and is the only order in which they can rationally
be studied. For this last there is an additional reason: since the more
special and complete sciences require not only the truths of the simpler
and more general ones, but still more their methods. The scientific
intellect, both in the individual and in the race, must learn in the
move elementary studies that art of investigation and those canons of