St Thomas om glädje

When we were treating of the passions, joy and sorrow proceed from love, but in contrary ways. For joy is caused by love, either through the presence of the thing loved, or because the proper good of the thing loved exists and endures in it; and the latter is the case chiefly in the love of benevolence, whereby a man rejoices in the well-being of his friend, though he be absent. On the other hand sorrow arises from love, either through the absence of the thing loved, or because the loved object to which we wish well, is deprived of its good or afflicted with some evil. Now charity is love of God, Whose good is unchangeable, since He is His goodness, and from the very fact that He is loved, He is in those who love Him by His most excellent effect, according to 1 John 4:16: "He that abideth in charity, abideth in God, and God in him." Therefore spiritual joy, which is about God, is caused by charity.