For Aristotle the distinguishing feature of humans is their ability to reason, which they get from their soul. Eg in plants the anima or soul produces the search for nourishment and food whereas in animals the anima produces the ability to move. Humans have these two characteristics but also the ability to reason. Humans are 'rational animals'. We should strive to achieve something better with our lives than simply living from pleasure to pleasure. Happiness for Aristotle is an activity of the soul