One of the lesser-known terms in Aristotle's ethical treatises is εὐπραξία (eupraxia) along with its sister εὐπραγία (eupragia). Both terms mean doing well, faring well, having success. Aristotle's use is connected to εὐδαιμονία, which he defines as "living well and doing well" (τὸ εὖ ζῆν καὶ τὸ εὖ πράττειν). But what are the metrics for "success" here? He leaves us several clues. First is the verb πράττειν, which for Aristotle means not merely engaging in activity but taking action, typically as the outcome of making a decision (this is why he thinks that, strictly speaking, animals and children do not "take action" even though they are clearly active physically and biologically). Second is that Aristotle contrasts εὐπραξία with εὐτυχία or good fortune; success is a matter of achievement, not luck.
This view of what it means to "do well" was not original with Aristotle but goes back to Socrates. In Book 3, Chapter 9 of his Memorabilia, Xenophon recounts a conversation in which someone asked Socrates what is the highest pursuit for a human being, to which Socrates replied: "Success" (εὐπραξία). When further questioned about the relationship between luck and success, Socrates explained that "success is to do something well by dint of learning and practice, and those who make this their pursuit seem to me to do well (εὖ πράττειν)".
Although Aristotle does not define things this way, I'm tempted to say that εὐδαιμονία is a combination of εὐπραξία (success at taking action) and εὐβουλία (success at making decisions). Interestingly, both terms appear more often in the Eudemian Ethics than in the Nicomachean Ethics: εὐβουλία is analyzed exclusively in what is traditionally known as NE VI.9, but as Anthony Kenny has shown that is actually EE V.9; and εὐπραξία/εὐπραγία is mentioned six times in the EE but only once in the NE. Whether this has import for the interpretation of the terms at issue (and εὐδαιμονία as a whole) remains to be seen - I plan to complete an in-depth comparison of the two treatises before I publish my forthcoming book Complete Yourself. Stay tuned for details...
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