The usual rejoinder to this argument is to fall back upon man's weakness and ignorance, and to take refuge in the infinite unknown. Man, it is said, may of course interfere a little with some of the less important laws of his being: but who is he, to grapple with the more vast and remote ones? Because he can prevent a pebble from falling, is he to suppose that he can alter the destiny of nations, and grapple forsooth with 'the eternities and the immensities,' and so forth? The argument is very powerful: but addrest rather to the imagination than the reason. It is, after all, another form of the old omne ignotum pro magnifico; and we may answer, I think fairly--About the eternities and immensities we know nothing, not having been there as yet; but it is a mere assumption to suppose, without proof, that the more remote and impalpable laws are more vast, in the sense of being more powerful (the only sense which really bears upon the argument), than the laws which are palpably at work around us all day long; and if we are capable of interfering with almost every law of human life which we know of already, it is more philosophical to believe (till disproved by actual failure) that we can interfere with those laws of our life which we may know hereafter. Whether it will pay us to interfere with them, is a different question. It is not prudent to interfere with the laws of health, and it may not be with other laws, hereafter to be discovered. I am only pleading that man can disobey the laws of his being; that such power has always been a disturbing force in the progress of the human race, which modern theories too hastily overlook; and that the science of history (unless the existence of the human will be denied) must belong rather to the moral sciences, than to that 'positive science' which seems to me inclined to reduce all human phaenomena under physical laws, hastily assumed, by the old fallacy of [Greek text], to apply where there is no proof whatsoever that they do or even can apply. As for the question of the existence of the human will--I am not here, I hope, to argue that. I shall only beg leave to assume its existence, for practical purposes. I may be told (though I trust not in this University), that it is, like the undulatory theory of light, an unphilosophical 'hypothesis.' Be that as it may, it is very convenient (and may be for a few centuries to come) to retain the said 'hypothesis,' as one retains the undulatory theory; and for the simple reason, that with it one can explain the phaenomena tolerably; and without it cannot explain them at all.