Moral Sciences are those concerned with the classifications and laws of action belonging to beings having Thoughts and Desires and Will. The most developed of these sciences at present are Metaphysics, Ethics, and Economics. Each of these is concerned with a single class of phenomena, which may be exactly conceived of and defined, and is open to the logical processes by which alone Sciences can be built up. But Induction cannot march up with quite so sure a stride, nor Deduction descend with so large degrees of certainty, in relation to _persons_ endowed with free-will, as in relation to physical substances held firm in the grip of unvaried law. Still, the doubt always attaches far more to the actions of an _individual_ than to the actions of the _masses_ of men. It is much easier to know human nature in general, than one man in particular, because many Inductions guided by observation and History make it almost certain how masses of men will act under a given set of conditions, while any one _may_ act in a contrary way. Deduction, accordingly, cannot hold quite the same place in the Moral Sciences so far as individuals are concerned, as it holds in the Physical and Exact Sciences; but this lack is perhaps more than made up by other advantages. _Experience_ in the moral sciences corresponds to _Experiments_ in the physical sciences. Then there is the great advantage of _Introspection_; since each man has within himself the means of interpreting and testing the inductions of Metaphysics, Ethics, and Economics. Then also there is the great resource of _Feigned Cases_, which, provided only they be cases possible to occur, open up to Reasoning a new means of proving and correcting. Besides these, which it enjoys in common with them, Economics, as we shall soon see, possesses one other great advantage over and above the rest of the Moral Sciences.