The belief that there is one and only one truth; those who espouse absolutism usually also believe that they know what this absolute truth is. In ethics, absolutism is usually contrasted to relativism.

An act utilitarian holds that an action is right or wrong according to the quantity of pleasure (hedonistic act utiltarian) or happiness (eudaimonistic act utilitarian) it produces.

The conviction that one simply does not know whether God exists or not; it is often accompanied with a further conviction that one need not care whether God exists or not.

A selfless concern for other people purely for their own sake. Altruism is usually contrasted with selfishness or egoism in ethics.

The Greek word for excellence or virtue. For the Greeks, this was not limited to human beings. A guitar, for example, has its arete in producing harmonious music, just as a hammer has its excellence or virtue in pounding nails into wood well. So, too, the virtue of an Olympic swimmer is in swimming well, and the virtue of a national leader lies in motivating people to work for the common good.

The belief that God does not exist. In the last two centuries, some of the most influential atheistic philosophers have been Karl Marx, Friedrich Nietzsche, Bertrand Russell, and Jean-Paul Sartre.

The ability to freely determine one's own course in life. Etymologically, it goes back to the Greek words for self and law. This term is most strongly associated with Immanuel Kant, for whom it meant the ability to give the moral law to oneself.