Nicene and Post-Nicene Fathers, Vol. IV:
Writings in Connection with the Manichæan Controversy.: Chapter 3

Chapter 3.—Happiness is in the Enjoyment of Man’s Chief Good.  Two Conditions of the Chief Good:  1st, Nothing is Better Than It; 2d, It Cannot Be Lost Against the Will.

4.  How then, according to reason, ought man to live?  We all certainly desire to live happily; and there is no human being but assents to this statement almost before it is made.  But the title happy cannot, in my opinion, belong either to him who has not what he loves, whatever it may be, or to him who has what he loves if it is hurtful or to him who does not love what he has, although it is good in perfection.  For one who seeks what he cannot obtain suffers torture, and one who has got what is not desirable is cheated, and one who does not seek for what is worth seeking for is diseased.  Now in all these cases the mind cannot but be unhappy, and happiness and unhappiness cannot reside at the same time in one man; so in none of these cases can the man be happy.  I find, then, a fourth case, where the happy life exists,—when that which is man’s chief good is both loved and possessed.  For what do we call enjoyment but having at hand the objects of love?  And no one can be happy who does not enjoy what is man’s chief good, nor is there any one who enjoys this who is not happy.  We must then have at hand our chief good, if we think of living happily.

5.  We must now inquire what is man’s chief good, which of course cannot be anything inferior to man himself.  For whoever follows after what is inferior to himself, becomes himself inferior.  But every man is bound to follow what is best.  Wherefore man’s chief good is not inferior to man.  Is it then something similar to man himself?  It must be so, if there is nothing above man which he is capable of enjoying.  But if we find something which is both superior to man, and can be possessed by the man who loves it, who can doubt that in seeking for happiness man should endeavor to reach that which is more excellent than the being who makes the endeavor.  For if happiness consists in the enjoyment of a good than which there is nothing better, which we call the chief good, how can a man be properly called happy who has not yet attained to his chief good? or how can that be the chief good beyond which something better remains for us to arrive at?  Such, then, being the chief good, it must be something which cannot be lost against the will.  For no one can feel confident regarding a good which he knows can be taken from him, although he wishes to keep and cherish it.  But if a man feels no confidence regarding the good which he enjoys, how can he be happy while in such fear of losing it?