Aristotle taught that virtue has to do with the proper function ("ergon") of a thing. An eye is only a good eye in so much as it can see, because the proper function of an eye is sight. Aristotle reasoned that humans must have a function specific to humans, and that this function must be an activity of the "psuchē" ("soul") in accordance with reason ("logos"). Aristotle identified such an optimum activity (the virtuous mean, between the accompanying vices of excess or deficiency) of the soul as the aim of all human deliberate action, "eudaimonia", generally translated as "happiness" or sometimes "well being". To have the potential of ever being happy in this way necessarily requires a good character ("ēthikē" "aretē"), often translated as moral or ethical virtue or excellence.