Diogenes Laertius reports that Zeno was the first to introduce the word ‘kathēkon’ and to write a treatise on the topic. He also suggests that, in connection with these reflections on kathēkonta, Zeno reversed Hesiod's well-known tag about the value of following good advice relative to that of knowing things for ourselves. According to Zeno,
The best man of all is the one who can accept another's sound advice,
Good also the man who knows all things for himself.
Although few things are so characteristic of the Stoics as their penchant for dispensing advice, Zeno's remark is initially rather puzzling. Surely, we might object, Hesiod is the one who has it right: merely following another's advice, whether in the form of specific individual instructions or more general rules, should hardly take precedence over knowing things for ourselves.
Zeno, however, apparently defended his own ranking by postulating a critical link between an ability to accept advice and action. A crucial prerequisite for praxis, he explained, is being capable of accepting and following the sound advice of others; by itself, knowing things on one's own holds no special guarantees with respect to one's actions. Yet, this added bit of explanation seems hardly less puzzling, especially given Zeno's overall endorsement of the Socratic claim that knowledge is sufficient for virtuous action.