What term refers to concise statements of principle, adages, or maxims that express common beliefs?

The term that refers to concise statements of principle, adages, or maxims that express common beliefs is "aphorisms." Aphorisms are often memorable phrases that convey wisdom or insight in a succinct manner, making them effective for expressing universal truths or moral lessons. For example, sayings like "Actions speak louder than words" encapsulate a broader truth in just a few words, illustrating the nature of aphorisms.

In contrast, chiasmus involves a rhetorical figure where elements are repeated in reverse order, which doesn’t inherently convey a principle or belief. Oxymoron refers to a figure of speech that combines contradictory terms, such as "bittersweet," and does not serve to express common beliefs. Extrapolation involves drawing conclusions based on incomplete data, which does not align with the nature of concise, principled expressions. Thus, "aphorisms" accurately captures the essence of the question.