Phronesis, or practical wisdom, or prudence, is, to me, a profound concept.  Aristotle identifies phronesis as one of the dianoetic virtues, that is, those intellectual virtues that characterize the well-ordered mind.  The dianoetic virtues are: Sophia (wisdom of first principles), episteme (scientific knowledge), phronesis (practical wisdom), techne (craft knowledge), and nous (intuition).  Phronesis is important to rhetoric in a variety of ways.  The links here each elucidate one facet of its importance.