Happiness has a beginning owing to the condition of the participator: but it has no end by reason of the condition of the good, the participation of which makes man happy.
 Thomas Aquinas, Summa Theologica (1274). copy citation

add
Author Thomas Aquinas
Source Summa Theologica
Topic happiness reason
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/17897/pg17897-images.html

Context

“The will can be directed to opposites, in things which are ordained to the end; but it is ordained, of natural necessity, to the last end. This is evident from the fact that man is unable not to wish to be happy. Reply Obj. 3: Happiness has a beginning owing to the condition of the participator: but it has no end by reason of the condition of the good, the participation of which makes man happy. Hence the beginning of happiness is from one cause, its endlessness is from another. ________________________ FIFTH ARTICLE [I-II, Q. 5, Art. 5] Whether Man Can Attain Happiness by His Natural Powers?” source