The Nebular Theory of Laplace has lately received far more confirmation than it needed, at the hands of the philosopher, Compte. These two have thus together shown—_not_, to be sure, that Matter at any period actually existed as described, in a state of nebular diffusion, but that, admitting it so to have existed throughout the space and much beyond the 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 that with which I am impressed by an hypothesis that not only reconciles these conditions, with mathematical accuracy, and reduces them into a consistent and intelligible whole, but