Although most economic agents allocate most of their resources to productive activities, sometimes individuals and groups live mainly or solely by appropriating from others. For example, at some stages of their histories the Vikings and the Mongols seem to have been pure predators. Other examples include individuals who specialize in being thieves and robbers. Under what conditions would an individual or a group choose to produce nothing and devote itself to preying on others?

Adam Smith (1776, Book V, Chapter 1, Part I) observed the relation between the relative wealth of nations and appropriative interactions.

The wealth of a richer agent gives a poor agent an incentive to prey on the richer agent and, perhaps, even to be a pure predator. Jack Hirshleifer (1991) provides an interesting example in which, if the relative endowment of an agent is sufficiently small, then that agent allocates all its resources to predatory activities.

This paper develops a general equilibrium model of appropriative interaction between two agents, a potential predator and the prey. The prey allocates its resources to the production of consumables and to defensive fortifications that serve to protect its property. The potential predator allocates its resources either to the production of consumables, or to offensive weapons that the predator uses to appropriate the prey's property, or to both.