II.-THE EPOCH OF COPERNICUS, GALILEO, AND
BACON.
Commencement of Modern Science.
On the first dawn of what is commonly called the revival of letters, after the
retrograde period of the dark ages, but which may be more properly designated as
the first commencement of civilisation in, at least, northern and western
Europe, science had evinced some signs of vitality, and even promising symptoms
of advance, while yet under the dominion of the Aristotelian schools.
The mathematical literature of the ancients was, perhaps, the first department
cultivated; and this, from the nature of the subject, could hardly excite much
suspicion or opposition. It was, however, the necessary precursor of the more
dangerous innovations which shortly followed in its train in the physical
branches.
System of Copernicus
The theory of Copernicus (1643) is a splendid monument of the power of simple
analogical, conjecture, when its course is in happy accordance with the great
principles of nature, to anticipate what the
labours of centuries of observation have been employed in confirming, and
transcendent mathematical skill in demonstrating. But its simplicity and unity are the characteristics which
peculiarly mark it out as connected with those
higher contemplations to which we are now referring. It opened the door to the
conception of one common cause of the planetary motions, of one universal
principle of order and arrangement pervading the system; --the first real glimpse
obtained of the true Cosmos.
Kepler
Within a century, this bold, if not wholly original, conception received
its great corroboration and extension in the grand discovery of the three laws
of planetary motion by Kepler, based on the accurate observations of Tycho
(1609-1618) and the mechanical and astronomical discoveries of Galileo, which
followed in rapid succession with the invention of the telescope, to verify and
extend the predictions of Copernicus.
Verbal disputes.
We have before noticed the extent to which the verbal spirit of the
Peripatetic logic had fixed itself in the intellect of the 15th and
16th centuries: so deeply had it taken root that we find the very same style of
argument sometimes adopted by the defenders as well as the assailants of the new
doctrines.
Thus, Nicolas of Cusa argued against the central position and fixity
of the earth that " since there is no circumference to the system there can
be no centre." And in the same strain, on the other side, the Sieur de
Beaulieu affirmed it to be a proposition absurd in geometry as it is against
faith and reason to make the circumference of a circle fixed while the centre is
moveable.
We cannot, however, be surprised at the slow progress made by such
novel ideas even among the more educated classes. The new theory seemed to
contradict the evidence of the senses; and as an eloquent writer has observed,
" the glorious deIusion of the rising and setting sun could not be
overcome." [ Mr. Everett's Address on the Opening of Albany
Observatory, U. S., 1856, p, 97.] All impressions, associations, and prejudices were arrayed
against the new doctrine, which only the few were even competent to understand.
Opposition to the Discoveries of Galileo.
In the disputes which arose as to the Copernican theory, and still more
extensively, half a century later, in
those which the discoveries of Galileo called forth, we trace the first decisive
conflict of the positive physical philosophy with the scholastic metaphysical
spirit of the age; and in the more serious hostility and persecution which it
encountered from the ecclesiastical authorities, we see the same antagonism with
the erroneous theological principles then maintained.
These events form,
perhaps, the first great epoch where we may contemplate the real influence which
the advance of physical discovery was beginning to exercise on subjects and
opinions, which, though of a different kind, could not fail to be materially
affected by the general movement.
Philosophical
and Theological Mysticism.
Philosophical
and Theological Mysticism.
The influence of the metaphysical forms of rea
soning, in those times adopted even in physical questions, directly cooperated
with the theologica I spirit of the age, in that they both tended to involve
the subject in mystery, which it is the distinguish ing character of the
inductive principle to clear away.
Thus, the single experimental fact exhibited
by Galileo, -- so utterly confounding to the Aristotelians, as by necessary
consequence it impugned their entire system, --that weights
of ten pounds and of one fell from the top of the tower at Pisa in exactly the
same time; and the simple reason that each of the ten must fall in exactly the
same time, --whether united in one mass or falling singly, however obvious in
itself, -- was highly important for dispelling the mysticising spirit which then
involved and obscured physical truth equally whether it rose from a
metaphysical or from a theological source.
Science Divested of Mystery
By this and other simple
experiments, Galileo divested the laws of mechanics of the
obscurity and confusion with which the Peripatetic system had invested them, and
prepared the way for the novel and startling doctrine that the same laws of
motion would apply to bodies in the heavens as to those on the earth.
After the
investigation of the simpler mechanical powers, from the date of the discoveries
of Archimedes, eighteen centuries elapsed before the solution of the problem, of
the inclined plane was effected by Stevinus: and the great algebraist Cardan
could not conceive the composition of forces: so entirely were the minds of men
incapacitated by confused metaphysical notions, which
mystified the plainest truths.
Slow Advance of Inductive Principles
It was thus long before the simple philosophical principles announced by Galileo obtained acceptance. Even Kepler did not acknowledge the sufficiency of the law of
inertia to preserve the motions of the planets; and imagined animal forces or
supernatural agency for the purpose. In other words, in accor dance with his
age, he did not apprehend the simple proposition that a body in motion must go
on till its motion is stopped or altered; and whatever stops or alters it is a
new force.
The followers of Copernicus long felt a difficulty as to the
preservation of the parallelism of the earth's axis, and imagined three distinct
motions impressed upon it, orbital, rotatory, axial; not understanding that the
third is a necessary part and consequence of the second.
The Peripatetic dogma
was that a body could only be moved by something in contact with it. They had
not attained the abstract notion of free motion retained after impulse. Hence
the main difficulty of the Copernican system to their minds. It was on this
ground that the Ptolemaists could only conceive the planets
as being carried round their orbits by the motion of the solid crystalline
spheres, like the hands of a clock; just as even at the present day we have
heard of some who fancy this to be the case with the moon. Nothing was more
difficult at first than to accept the simpler idea of free motion under the
influence of cosmical forces; or to appreciate the analogy of all the celestial
motions, as being of the same kind, or the connection of impulsive with rotatory
force.
Such Instances are important, as they point to the necessity for clearing
the subject of all obscurity of ideas whether of a metaphysical or supernatural
kind; if we would adhere to the simplicity of nature, and above all, of seizing
upon just analogy as the true key to the unity of principle and harmony of
causation pervading the whole.
The
Order of Nature
