What Is Aggression?
April 27, 2010
The following essay was my submission for an ATP 101 assignment asking: What is aggression? How can we distinguish between aggression and other kinds of undesirable influence? The space in the assignment was limited so I only intend this to be a starting point for further research.
A key concept underlying aggression is that of a moral agent’s ‘boundary’. I do not mean for this term to imply a continuous, spatiotemporal boundary  , though it will often correspond to exactly that. Instead, the boundary is a logical entity that divides the set of all actions that can be performed by others into (a) those that treat our agent as a means  (“inside the boundary”) and (b) those that do not (“outside the boundary”).
Simply performing an action that treats another person as a means (i.e. is within that person’s boundary) is not sufficient to make the action one of aggression, however. That would count most, if not all, of human interaction as aggressive, making it a poor basis for a legal system  . Therefore, we might be tempted to separate out those ‘boundary crossings’ that occur without the consent of our agent. But that too seems a poor basis for a legal system that needs to enforce its judgment without being itself unjust.
I do think, however, that lack of consent from our agent is a necessary (but not sufficient) condition for an action committed against her to be classed as one of aggression. Either of two other conditions must obtain: (a) the action is not necessary to end an act of aggression on the moral agent’s part; or (b) the action is necessary to end an act of aggression but morally disproportionate (in the direction of excess) to the seriousness of that act. Therefore, aggression is treating someone as a means without their consent where doing so is either (a) unnecessary to end aggression or (b) disproportionate to the seriousness of that aggression  . (Long) We might call this, and therefore define aggression as, “treating someone as a mere means.”
Because I have given a definition that relies on the concept of “treating someone as a means,” using it to distinguish between aggression and other kinds of undesirable influence will require a method for knowing what “treating someone as a means” means. It also relies on an ability to determine the necessity of an action (to end aggression) and whether an action found so necessary is disproportionate in moral seriousness. The necessity of an action to end aggression is likely something that can be determined empirically, for the most part. The other two factors will require more complex methods of determination (e.g. critical reflection, reflective equilibrium, intuition-pumping, additional moral principles, community norms etc.)
I will say something further about “treating someone as a means.” I do not think that treating someone as a means requires intention. Nevertheless, intention can play a role in certain contexts, e.g. “threatening to invade someone’s boundary is itself an invasion of that person’s boundary (since in announcing my intention of using you as a means I am already treating you as the sort of thing it is legitimate to use as a means).” (Long) I do think it requires subjecting or subordinating someone to some condition, rather than simply taking advantage of the facts about someone.
You will notice that I do not refer to property rights nor do I specifically refer to physical force. It may be the case (and I think there are good reasons for thinking) that in the process of unpacking ‘treating someone as a means’ that it will necessitate some consideration of external property and/or a limit to actions that are physical violations of person or property. This more general definition, however, keeps the underlying moral premise in the foreground so as to prevent any question-begging formulations prior to a discussion of property rights or non-physical harm among those who share a desire to capture the spirit of non-aggression.
Long, Roderick T. “Abortion, Abandonment, and Positive Rights: The Limits of Compulsory Altruism.” 1993. <http://praxeology.net/RTL-Abortion.htm>.
 Imagine a sphere in 4D space-time surrounding our moral agent.
 I will not be defending this notion here but it comes from (though not only from) the Aristotelian virtue-ethical normative principle that states that, “Every person has the right not to be treated as a mere means to the ends of others,” where ‘right’ is understood to mean in the sense of ‘legally enforceable’. To treat someone like a mere means is to not treat them as an end in themselves. (Long)
 I will only focus on aggression as it relates to legal institutions concerned with the legitimate use of force. There are many other domains concerned with correctly defining ‘aggression’, including psychology and biology, but these are not generally concerned with the normative realm implied by a non-aggression principle.
 The recursive nature of this definition is not problematic because (a) obtains in the case where there is simply a lack of any reciprocal boundary crossing.