First, from the general notion of happiness.  For since happiness is a “perfect and sufficient good,” it excludes every evil, and fulfils every desire.  But in this life every evil cannot be excluded.  For this present life is subject to many unavoidable evils; to ignorance on the part of the intellect; to inordinate affection on the part of the appetite, and to many penalties on the part of the body; as Augustine sets forth in De Civ.  Dei xix, 4.  Likewise neither can the desire for good be satiated in this life.  For man naturally desires the good, which he has, to be abiding.  Now the goods of the present life pass away; since life itself passes away, which we naturally desire to have, and would wish to hold abidingly, for man naturally shrinks from death.  Wherefore it is impossible to have true Happiness in this life.

Secondly, from a consideration of the specific nature of Happiness, viz. the vision of the Divine Essence, which man cannot obtain in this life, as was shown in the First Part (Q. 12, A. 11).  Hence it is evident that none can attain true and perfect Happiness in this life.

Reply Obj. 1:  Some are said to be happy in this life, either on account of the hope of obtaining Happiness in the life to come, according to Rom. 8:24:  “We are saved by hope”; or on account of a certain participation of Happiness, by reason of a kind of enjoyment of the Sovereign Good.

Reply Obj. 2:  The imperfection of participated Happiness is due to one of two causes.  First, on the part of the object of Happiness, which is not seen in Its Essence:  and this imperfection destroys the nature of true Happiness.  Secondly, the imperfection may be on the part of the participator, who indeed attains the object of Happiness, in itself, namely, God:  imperfectly, however, in comparison with the way in which God enjoys Himself.  This imperfection does not destroy the true nature of Happiness; because, since Happiness is an operation, as stated above (Q. 3, A. 2), the true nature of Happiness is taken from the object, which specifies the act, and not from the subject.

Reply Obj. 3:  Men esteem that there is some kind of happiness to be had in this life, on account of a certain likeness to true Happiness.  And thus they do not fail altogether in their estimate. ________________________

FOURTH ARTICLE [I-II, Q. 5, Art. 4]

Whether Happiness Once Had Can Be Lost?

Objection 1:  It would seem that Happiness can be lost.  For Happiness is a perfection.  But every perfection is in the thing perfected according to the mode of the latter.  Since then man is, by his nature, changeable, it seems that Happiness is participated by man in a changeable manner.  And consequently it seems that man can lose Happiness.

Obj. 2:  Further, Happiness consists in an act of the intellect; and the intellect is subject to the will.  But the will can be directed to opposites.  Therefore it seems that it can desist from the operation whereby man is made happy:  and thus man will cease to be happy.