But here an objection may be raised. “What is the use of them?” it may be asked. Wisdom does not consider what tends to make man happy (for it does not ask how anything is brought about). Prudence indeed does this, but why do we need it? Prudence is the faculty which deals with what is just and noble and good for man, i.e. with those things which it is the part of the good man to do; but the knowledge of them no more makes us apter to do them, if (as has been said) the [moral] virtues are habits, than it does in the case of what is healthy and wholesome⁠—healthy and wholesome, that is, not in the sense of conducing to, but in the sense of issuing from, a healthy habit; for a knowledge of medicine and gymnastics does not make us more able to do these things.