The significance of Aristotle for Western thought was the way he brought speculative philosophy into the realm of practical action. Aristotle wrote on physics, biology, astronomy, medicine, geography, aesthetics, ethics, government, psychology, poetry and theology. His conception of logic dominated Western thought until the late 19th century, with the introduction of mathematical logic.

For Aristotle, the Good in human life was that toward which all human actions and decisions aim. The Goods of primary interest to Aristotle were things good in themselves, complete without qualification. Examples include intelligence and honor. Such things are aimed at because of what they are rather than because of what they contribute to some other aim.

The highest Good for Aristotle is clearly happiness, which more than anything else is complete without qualification. Happiness depends on two things: (1) having enough money and (2) developing virtue. The supreme virtue for Aristotle is the understanding. The understanding is something that is active and pleasurable.  It is also an expression of that in the human being which is fine, noble and magnanimous.

This highest Good, which is thus a combination of happiness and understanding, pleasure and activity, however, does not have a single form. It must be the sort of thing an individual can both pursue and possess. It cannot be an Idea common to all good things. Rather it is a Substance, intrinsic to the values and dispositions of an individual.