Stobaeus on Stoic Ethics 20

Again, of good things, some are worth choosing for their own sakes, whereas some are instrumental. 

All those which are subject to reasonable choice for the sake of nothing else are worth choosing for their own sakes, whereas those which are subject to reasonable choice because they produce other things are said to be worth choosing in the instrumental sense. 

IMAGE: John Everett Millais, The Pearl of Great Price (1864)