which was a more
mischievous thief of my time, in proportion as it was supported by the
authority of all philosophers, and apparently agreeable to metaphysics."

[Sidenote: The philosophical import of these laws.] The philosophical
significance of Kepler's discoveries was not recognized by the
ecclesiastical party at first. It is chiefly this, that they constitute
a most important step to the establishment of the doctrine of the
government of the world by law. But it was impossible to receive these
laws without seeking for their cause. The result to which that search
eventually conducted not only explained their origin, but also showed
that, as laws, they must, in the necessity of nature, exist. It may be
truly said that the mathematical exposition of their origin constitutes
the most splendid monument of the intellectual power of man.

[Sidenote: Necessity for mechanical science.] Before the heliocentric
theory could be developed and made to furnish a clear exposition of the
solar system, which is obviously the first step to just views of the
universe, it was necessary that the science of mechanics should be
greatly improved--indeed, it might be said, created; for during those
dreary ages following the establishment of Byzantine power, nothing had
been done toward the acquisition of correct views either in statics or
dynamics. It was impossible that Europe, in her lower states of life,
could produce men capable of commencing where Archimedes had left off.
She had to wait for the approach of her Age of Reason for that.

[Sidenote: Leonardo da Vinci.] The man of capacity at last came.
Leonardo da Vinci was born A.D. 1452. The historian Hallam, enumerating
some of his works, observes, "His knowledge was almost preternatural."
Many of his writings still remain unpublished. Long before Bacon, he
laid down the maxim that experience and observation must be the
foundation of all reasoning in science; that experiment is the only
interpreter of nature, and is essential to the ascertainment of laws.
Unlike Bacon, who was ignorant of mathematics, and even disparaged them,
he points out their supreme advantage. Seven years after the voyage of
Columbus, this great man--great at once as an artist, mathematician, and
engineer--gave a clear exposition of the theory of forces obliquely
applied on a lever; a few years later he was well acquainted with the
earth's annual motion. He knew the laws of friction, subsequently
demonstrated b