Yet a law of nature remains merely the observed rule according to
which nature invariably proceeds whenever certain definite circumstances
occur. Therefore a law of nature may be defined as a fact expressed
generally—_un fait généralisé_—and thus a complete enumeration of all the
laws of nature would only be a complete register of facts. The
consideration of nature as a whole is thus completed in _morphology_,
which enumerates, compares, and arranges all the enduring forms of
organised nature. Of the causes of the appearance of the individual
creature it has little to say, for in all cases this is procreation (the
theory of which is a separate matter), and in rare cases the _generatio
æquivoca_. But to this last belongs, strictly speaking, the manner in
which all the lower grades of the objectification of will, that is to say,
physical and chemical phenomena, appear as individual, and it is precisely
the task of etiology to point out the conditions of this appearance.
Philosophy, on the other hand, concerns itself only with the universal, in
nature as everywhere else. The original forces themselves are here its
object, and it recognises in them the different grades of the objectivity
of will, which is the inner nature, the “in-itself” of this world; and
when it regards the world apart from will, it explains it as merely the
idea of the subject. But if etiology, instead of preparing the way for
philosophy, and supplying its doctrines with practical application by
means of instances, supposes that its aim is rather to deny the existence
of all original forces, except perhaps _one_, the most general, for
example, impenetrability, which it imagines it thoroughly understands, and
consequently seeks forcibly to refer all the others to it—it forsakes its
own province and can only give us error instead of truth. The content of
nature is supplanted by its form, everything is ascribed to the
circumstances which work from without, and nothing to the inner nature of
the thing. Now if it were possible to succeed by this method, a problem in
arithmetic would ultimately, as we have already remarked, solve the riddle
of the universe. But this is the method adopted by those, referred to
above, who think that all physiological effects ought to be reduced to
form and combination, this, perhaps, to electricity, and this again to
chemism, and chemism to mechanism. The mistake of Descartes, for example,
and of all the Atomists, was of this last description. They referred the
movements of the globe to the impact of a fluid, and the qualities of
matter to the connection and form of the atoms, and hence they laboured to
explain all the phenomena of nature as merely manifestations of
impenetrability and cohesion. Although this has been given up, precisely
the same error is committed in our own day by the electrical, chemical,
and mechanical physiologists, who obstinately attempt to explain the whole