The different intellectual excellences just named—­Considerateness, Sagacity, Prudence [Greek:  phronaesis], and Intellect [Greek:  Nous], seem all to bear on the same result, and are for the most part predicable of the same individuals.  All of them are concerned with the ultimate applications of principle to practice, and with the actual moments for decision and action.  Indeed, Intellect [Greek:  Nous] deals with the extremes at both ends of the scale:  with the highest and lowest terms.  In theoretical science, it apprehends and sanctions the major propositions, the first and highest principia of demonstrations:  in practical dealings, it estimates the minor propositions of the syllogism, the possibilities of the situation, and the ultimate action required.  All these are the principia from whence arises the determining motive:  for the universal is always derived from particulars; these we must know through sensible perception, which is in this case the same thing as intellect [Greek:  Nous].  Intellect is in fact both the beginning and the end:  it cognizes both the first grounds of demonstration and the last applications of the results of demonstration.  A man cannot acquire science by nature, or without teaching:  but he may acquire Intellect and Sagacity by nature, simply through, long life and abundant experience.  The affirmations and opinions of old men deserve attention, hardly less than demonstrations:  they have acquired an eye from experience, and can thus see the practical principles (though they may not be able to lay out their reasons logically) (XI.).

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.).