In the context of Dung's theory of abstract argumentation frameworks, the comparison between different semantics is often carried out by resorting to some specific examples considered particularly meaningful. This kind of comparison needs to be complemented by more general evaluation criteria based on “example-independent” basic principles. We review several principles for argumentation semantics, identify their formal counterpart in terms of extensions, and analyze their relationships with the notion of argument justification state. Then, we evaluate and compare several semantics on the basis of the introduced principles.