space now occupied by our solar system, _and to have
commenced a movement towards a centre_--it must gradually have assumed
the various forms and motions which are now seen, in that system, to
obtain. A demonstration such as this--a dynamical and mathematical
demonstration, as far as demonstration can be--unquestionable and
unquestioned--unless, indeed, by that unprofitable and disreputable
tribe, the professional questioners--the mere madmen who deny the
Newtonian law of Gravity on which the results of the French
mathematicians are based--a demonstration, I say, such as this, would to
most intellects be conclusive--and I confess that it is so to mine--of the
validity of the nebular hypothesis upon which the demonstration depends.

That the demonstration does not _prove_ the hypothesis, according to the
common understanding of the word "proof," I admit, of course. To show
that certain existing results--that certain established facts--may be,
even mathematically, accounted for by the assumption of a certain
hypothesis, is by no means to establish the hypothesis itself. In other
words:--to show that, certain data being given, a certain existing result
might, or even _must_, have ensued, will fail to prove that this result
_did_ ensue, _from the data_, until such time as it shall be also shown
that there are, _and can be_, no other data from which the result in
question might _equally_ have ensued. But, in the case now discussed,
although all must admit the deficiency of what we are in the habit of
terming "proof," still there are many intellects, and those of the
loftiest order, to which _no_ proof could bring one iota of additional
_conviction_. Without going into details which might impinge upon the
Cloud-Land of Metaphysics, I may as well here observe that the force of
conviction, in cases such as this, will always, with the right-thinking,
be proportional to the amount of _complexity_ intervening between the
hypothesis and the result. To be less abstract:--The greatness of the
complexity found existing among cosmical conditions, by rendering great
in the same proportion the difficulty of accounting for all these
conditions _at once_, strengthens, also in the same proportion, our
faith in that hypothesis which does, in such manner, satisfactorily
account for them:--and as _no_ complexity can well be conceived greater
than that of the astronomical conditions, so no conviction can be
stronger--to _my_ mind at least--than