Kant's mode of dealing with the doctrine of necessity is very singular. That the phenomena of the mind follow fixed relations of cause and effect is, to him, as unquestionable as it is to Hume. But then there is the Ding an sich, the Noumenon, or Kantian equivalent for the substance of the soul. This, being out of the phenomenal world, is subject to none of the laws of phenomena, and is consequently as absolutely free, and as completely powerless, as a mathematical point, in vacua, would be. Hence volition is uncaused, so far as it belongs to the noumenon; but, necessary, so far as it takes effect in the phenomenal world.
Since Kant is never weary of telling us that we know nothing whatever, and can know nothing, about the noumenon, except as the hypothetical subject of any number of negative predicates; the information that it is free, in the sense of being out of reach of the law of causation, is about as valuable as the assertion that it is neither grey, nor blue, nor square. For practical purposes, it must be admitted that the inward possession of such a noumenal libertine does not amount to much for people whose actual existence is made up of nothing but definitely regulated phenomena. When the good and evil angels fought for the dead body of Moses, its presence must have been of about the same value to either of the contending parties, as that of Kant's noumenon, in the battle of impulses which rages in the breast of man. Metaphysicians, as a rule, are sadly deficient in the sense of humour; or they would surely abstain from advancing propositions which, when stripped of the verbiage in which they are disguised, appear to the profane eye to be bare shams, naked but not ashamed.
CHAPTER XI.
THE PRINCIPLES OF MORALS.
In his autobiography, Hume writes:—
"In the same year [1752] was published at London my Inquiry Concerning the Principles of Morals; which in my own opinion (who ought not to judge on that subject) is of all my writings, historical, philosophical, and literary, incomparably the best. It came unnoticed and unobserved into the world."
It may commonly be noticed that the relative value which an author ascribes to his own works rarely agrees with the estimate formed of them by his readers; who criticise the products, without either the power or the wish to take into account the pains which they may have cost the producer. Moreover, the clear and dispassionate common sense of the Inquiry concerning the Principles of Morals may have tasted flat after the highly-seasoned Inquiry concerning the Human Understanding. Whether the public like to be deceived, or not, may be open to question; but it is beyond a doubt that they love to be shocked in a pleasant and mannerly way. Now Hume's speculations on moral questions are not so remote from those of respectable professors, like Hutcheson, or saintly prelates, such as Butler, as to present any striking novelty. And they support the cause of righteousness in a cool, reasonable, indeed slightly patronising fashion, eminently in harmony with the mind of the eighteenth century; which admired virtue very much, if she would only avoid the rigour which the age called fanaticism, and the fervour which it called enthusiasm.
Having applied the ordinary methods of scientific inquiry to the intellectual phenomena of the mind, it was natural that Hume should extend the same mode of investigation to its moral phenomena; and, in the true spirit of a natural philosopher, he commences by selecting a group of those states of consciousness with which every one's personal experience must have made him familiar: in the expectation that the discovery of the sources of moral approbation and disapprobation, in this comparatively easy case, may furnish the means of detecting them where they are more recondite.