such a time,
there is no reason to doubt, but every reason to conclude, that the
evolution of matter, as we now know it, was accomplished in accordance with
law. Similarly, we are not concerned with the question as to how the law of
gravitation came to be associated with matter; for it is overwhelmingly
probable, from the extent of the analogy, that if our knowledge concerning
molecular physics were sufficiently great, the existence of the law in
question would be found to follow as a necessary deduction from the primary
qualities of matter and force, just as we can now see that, when present,
its peculiar quantitative action necessarily follows from the primary
qualities of space.

Starting, then, with these data,--matter, force, and the law of
gravitation,--what must happen? We have the strongest scientific reason to
believe that the matter of the solar system primordially existed in a
highly diffused or nebulous form. By mutual gravitation, therefore, all the
substance of the nebula must have begun to concentrate upon itself, or to
condense. Now, from this point onwards, I wish it to be clearly understood
that the mere consideration of the supposed facts not admitting of
scientific proof, or of scientific explanation if true, in no wise affects
the certainty of the doctrine which these facts are here adduced to
establish. Fully granting that the alleged facts are not beyond dispute,
and that, even if true, innumerable other unknown and unknowable facts must
have been associated with them--fully admitting, in short, that our ideas
concerning the genesis of the solar system are of the crudest and least
trustworthy character; still, if it be admitted, what at the present day
only ignorance or prejudice can deny, viz., that, as a whole, evolution has
been the method of the universe; then it follows that the doctrine here
contended for is as certainly true as it would be were we fully acquainted
with every cause and every change which has acted and ensued throughout the
whole process of the genesis of things.

Now, bearing this caveat in mind, we have next to observe that when once
the nebula began to condense, new relations among its constituent parts
would, _for this reason_, begin to be established. "Given a rare and widely
diffused mass of nebulous matter,... what are the successive changes that
will take place? Mutual gravitation will approximate its atoms, but their
approximation will be opposed by atomic repulsion