to follow, as it were, in the leading-strings of nature, but must proceed
in advance with principles of judgement according to unvarying laws,
and compel nature to reply its questions. For accidental observations,
made according to no preconceived plan, cannot be united under a
necessary law. But it is this that reason seeks for and requires. It
is only the principles of reason which can give to concordant
phenomena the validity of laws, and it is only when experiment is
directed by these rational principles that it can have any real
utility. Reason must approach nature with the view, indeed, of
receiving information from it, not, however, in the character of a
pupil, who listens to all that his master chooses to tell him, but
in that of a judge, who compels the witnesses to reply to those
questions which he himself thinks fit to propose. To this single
idea must the revolution be ascribed, by which, after groping in the
dark for so many centuries, natural science was at length conducted
into the path of certain progress.

We come now to metaphysics, a purely speculative science, which
occupies a completely isolated position and is entirely independent
of the teachings of experience. It deals with mere conceptions--not,
like mathematics, with conceptions applied to intuition--and in it,
reason is the pupil of itself alone. It is the oldest of the sciences,
and would still survive, even if all the rest were swallowed up in
the abyss of an all-destroying barbarism. But it has not yet had the
good fortune to attain to the sure scientific method. This will be
apparent; if we apply the tests which we proposed at the outset. We
find that reason perpetually comes to a stand, when it attempts to
gain a priori the perception even of those laws which the most
common experience confirms. We find it compelled to retrace its
steps in innumerable instances, and to abandon the path on which it