The Metaphysical Elements of Ethics by Immanuel Kant Chapter 13 Page 3

Secondly. The difference between virtue and vice cannot be sought in the degree in which certain maxims are followed, but only in the specific quality of the maxims (their relation to the law). In other words, the vaunted principle of Aristotle, that virtue is the mean between two vices, is false. * For instance, suppose that good management is given as the mean between two vices, prodigality and avarice; then its origin as a virtue can neither be defined as the gradual diminution of the former vice (by saving), nor as the increase of the expenses of the miserly. These vices, in fact, cannot be viewed as if they, proceeding as it were in opposite directions, met together in good management; but each of them has its own maxim, which necessarily contradicts that of the other.

* The common classical formulae of ethics- medio