The third definition is an attempt to operationalize the notion of aggression; it has an empirical component lacking in other explanations. The implicit assumption is that the only way rights can be violated is by using violence - interpersonal force - or threatening to. "Person" should be interpreted as an individual and his property. The abstract notion of rights is made concrete by observing who struck first, or who fired the first shot. This formulation of aggression was proposed by Ayn Rand, and allows a bridge from theory to practice. But one must be careful: empirical observation alone cannot determine whether aggression occurred. History is a critical consideration. If someone sees Ms. Smith forcibly taking a watch from Mr. Jones, one cannot know whether aggression has taken place unless one knows the history of the watch. Perhaps it rightfully belongs to Smith, and Jones stole it from her yesterday.

political power - aggression perpetrated by the state, or the ability to engage in such aggression.

At the concrete level, the different anarchist schools have numerous disagreements over what constitutes aggression. This is a natural consequence of their different conceptions of just property. On a conceptual level, with the different property systems abstracted away, aggression is the central commonality of all forms of anarchism. Anarchism opposes the state because it is an instrument of legitimized aggression.

Virtually all anarchists base their political position upon the ethical principle of non-aggression. The critique of the institution of state, analysis of economic systems, authority, hierarchies, and so on all come down to the question of whether it constitutes or necessitates aggression. The way hot-button words like "exploitation," "wage slavery, "usary," "free trade" and "voluntary exchange" are understood ultimately comes down to whether these respective practices are seen as aggression or not.

non-aggression principle (NAP) - in the context of civilized society, aggression is morally wrong.

The hedge "in the context of civilized society" attempts to qualify the principle enough to account for emergency situations ("lifeboat ethics"), otherwise a rich source of counterexamples. If we restrict the NAP to an ethical environment where physical survival is not an issue (the realm of man qua civilized man), it seems to hold up splendidly. This implies a kind of middle way for ethical principles, neither absolutism nor relativism. It acknowledges that different life situations may require different principles of conduct. This restricted relativism might be called "modal absolutism."