Finally, this concept appears in certain familiar phrases, such as “by virtue of,” “in virtue of,” and the like, where it usually connotes _strength_, or _efficacy_, or even _reason_, and _right_. Thus we see that the word “virtue,” like the other ethical concepts we have analysed, loses almost all of its specificity when it enters into idiomatic phrases. These four classes exhaust the uses to which this concept has been put. What, then, shall we declare to be the common element in them which we may call the essence of virtue with respect to human beings? In giving our answer, it is necessary to call attention to the fact that our third use of the word “virtue” (signifying the medicinal efficacy of drugs) will occupy a minor, or even negligible place in our definition. As for the rest, seeing that the virtues are one and all traits which are commended or praised, they may be considered as action-patterns or action-tendencies which human beings manifest. We can also go further than this. Employing the physiological principles hitherto used in defining ethical concepts, it appears at once that the word “virtue” means that _energy is either being mobilized or expended to obtain what the organism considers to be a dependable good_. This can also be stated in another way, by saying that those human traits which have been expressly denominated virtues are some of the attributes of what is commonly called a “good” man. (See Ex. 21, p. 38.) In this restricted sense, furthermore, the _virtuous_, or _good_, man is the one whose acts are called _right_. And this leads us at once to a very important question. Why is it, we ask, that so few of the innumerable human traits that are commended every day—not only by words of praise, but also by that subtler and more emphatic sign of unconscious imitation—have been chosen as virtues, while so many others have been left out of the list? The four cardinal virtues,—courage, prudence, temperance, and justice,—exemplify this high degree of selectiveness, while this inventory omits all mention of human skill in any form, in spite of the fact that when the list was made by Plato, human skill in the fine arts had reached one of its limits of excellence.