Stobaeus on Stoic Ethics 22

Again, of good things some consist in motion and some consist in a state. 

For such things as joy, good spirits, and temperate conversation consist in motion, whereas such things as a well-ordered quietude, undisturbed rest, and a manly attention consist in a state. 

Of things which consist in a state, some also consist in a condition, such as the virtues; others are only in a state, such as the above mentioned. 

Not only the virtues consist in a condition, but also the crafts which are transformed in the virtuous man by his virtue and so become unchangeable; for they become quasi-virtues. 

And they say that the so-called practices are also among the goods which consist in a condition, such as love of music, love of letters, love of geometry, and the like. 

For there is a method which selects those elements in such crafts which have an affinity to virtue, by referring them to the goal of life. 

IMAGE: Albrecht Dürer, St. Jerome in His Study (1514)