Summum bonum (Latin for the highest good) is an expression used in philosophy, particularly in medieval philosophy and in the philosophy of Immanuel Kant, to describe the ultimate importance, the singular and most ultimate end which human beings ought to pursue. The summum bonum is generally thought of as being an end in itself, and at the same time containing all other goods. In Christian philosophy, the highest good is usually defined as the life of the righteous, the life led in Communion with God and according to God's precepts.
The concept, as well as the philosophical and theological consequences drawn from the purported existence of a more or less clearly defined summum bonum, could be traced back to the earliest forms of monotheism: for instance, Zoroastrianism and Judaism. In the Western world, the concept was introduced by the neoplatonic philosophers, and described as a feature of the Christian God by Saint Augustine in De natura boni (On the Nature of Good, written circa 399). Augustine denies the positive existence of absolute evil, describing a world with God as the supreme good at the center, and defining different grades of evil as different stages of remoteness from that center.
Experience soon teaches that all desires cannot be satisfied, that they are conflicting, and that some goods must be foregone in order to secure others. Hence the necessity of weighing the relative value of goods, of classifying them, and of ascertaining which of them must be procured at the loss of others. The result is the division of goods into two great classes, the physical and the moral, happiness and virtue. Within either class it is comparatively easy to determine the relation of particular good things to one another, but it has proved far more difficult to fix the relative excellence of the two classes of virtue and happiness.
Judgments on the highest good have generally fallen into four categories:
The Wiktionary entry for summum bonum