Indeed, it appears to be by no means improbable that this peculiarity of Hume's moral constitution was the cause of his gradually forsaking philosophical studies, after the publication of the third part (_On Morals_) of the _Treatise_, in 1740, and turning to those political and historical topics which were likely to yield, and did in fact yield, a much better return of that sort of success which his soul loved.

The _Philosophical Essays Concerning the Human Understanding_, which afterwards became the _Inquiry_, is not much more than an abridgment and recast, for popular use, of parts of the _Treatise_, with the addition of the essays on Miracles and on Necessity.

In style, it exhibits a great improvement on the _Treatise_; but the substance, if not deteriorated, is certainly not improved.

Hume does not really bring his mature powers to bear upon his early speculations, in the later work.

The crude fruits have not been ripened, but they have been ruthlessly pruned away, along with the branches which bore them.