Mimetic appetite is a way to describe the power of mimesis as a kind of passion, to take a category from classical metaphysics. According to Thomas Aquinas, humans and the rest of creation have appetites that drive them toward their telos, or ultimate ends. Humans, though, are more complicated than any other kind of being because they have three different kinds of appetites.
Inanimate and vegetative beings have natural appetites; animals have both natural and sense appetites; and God and angels have intellectual appetites. Only humans have all three. The mimetic appetite, it could be argued, would be a kind of fourth appetite—something unique to humans which drives their desires not only due to the intellect but a power of imitation which makes them want what other people want. Different people can have differing levels of mimetic appetite. Often times the mimetic appetite in a person can be so strong so as to override their intellectual appetite.
There is a general mimetic appetite that every human person has. But there can be specific mimetic appetites for certain things—for instance a mimetic appetite for marriage, in which the desire of men and women to get married is mutually reinforcing.
In Thomistic metaphysics, the function of the passions is not to decide upon a course of action but to respond to stimuli and prompt the human person to act according to the face value of those stimuli. Then the passions defer to the judgment of reason because only the rational appetite can command human action and because the sense analysis concludes that acting on a certain prompting of the passions is not conducive to final happiness. In the mimetic appetite, though, as conceived by some Girardians, this principle would not hold. The intellect itself may be more or less mimetic depending on the strength of the mimetic appetite.
The passions respond to intentional objects—not objects considered in themselves (material objects). For instance, the passion to steal a purse is not focused on the object of a purse itself; the object of that action is to take, secretly, another person’s property for one’s personal enrichment. The purse, as an object in and of itself, is not the important thing.The purse could be blue, gold, or orange. It could contain $100 or $500. These facts are somewhat incidental to the intentional object of the action.
In the case of the mimetic appetite, the intentional object is apparently the acquisition of some object that is mediated by a model; the real intentional object is the acquisition of some quality of being that the imitator presumes is possessed by the model. The object is merely an accident in this pursuit.