But an objector may ask--Of what use are Philosophy and Prudence? He may take such grounds as these. (1) Philosophy has no practical aim at all; nor does it consider the means of happiness? (2) Prudence, though bearing on practice, is merely knowledge, and does not ensure right action. (3) Even granting the knowledge to be of value as direction, it might be obtained, like medical knowledge, from a professional adviser. (4) If philosophy is better than prudence, why does prudence control philosophy? We have to answer these doubts. The first is answered by asserting the independent value of philosophy and prudence, as perfections of our nature, and as sources of happiness in themselves. The second and third doubts are set at rest, by affirming prudence to have no existence apart from virtue. Without a virtuous aim, there is no such thing as Prudence: there is nothing but cleverness degenerating into cunning; while virtue without virtuous prudence is nothing better than a mere instinct, liable to be misguided in every way (XII.).
There is one more difficulty to be cleared up respecting virtue. All our dispositions; and therefore all our ethical excellences, come to us in a certain sense by nature; that is, we have from the moment of birth a certain aptitude for becoming temperate, courageous, just, &c. But these natural aptitudes or possessions [Greek: physikai hexeis] are something altogether distinct from the ethical excellences proper, though capable of being matured into them, if intellect and prudence be superadded. Sokrates was mistaken in resolving all the virtues into prudence; but he was right in saying that none of them can exist without prudence. The virtues ought to be defined as, not merely ethical dispositions _according_ to right reason, but ethical dispositions _along with_ right reason or prudence (_i.e._, prudence is an ever present co-efficient). It is thus abundantly evident that none but a prudent man can be good, and none but a good man can be prudent. The virtues are separable from each other, so far as the natural aptitudes are concerned: a man may have greater facility for acquiring one than another. But so far as regards the finished acquirements of excellence, in virtue of which a man is called _good_--no such separation is possible. All of them alike need the companionship of Prudence (XIII.).