Instantiation principle

The principle of instantiation or principle of exemplification is the concept in metaphysics and logic that there can be no uninstantiated or unexemplified properties (or universals). In other words, it is impossible for a property to exist which is not had by some object. Aristotle is well known for endorsing the principle and Plato for denying it.

Consider a chair. Presumably chairs did not exist 150,000 years ago. Thus, according to the Principle of Instantiation, the property of being a chair did not exist 150,000 years ago either. Similarly (and assuming objects are colored), if all red objects were to suddenly go out of existence, then the property of being red would likewise go out of existence.

To make the Principle of Instantiation more plausible in the light of these examples, the existence of properties or universals is not tied to their actual existence now, but to their existence in space-time considered as a whole. Thus, any property which is instantiated, has been instantiated, or will be instantiated exists. The property of being red would exist even if all red things were to be destroyed, because it has been instantiated. This broadens the range of properties which exist if the principle is true.

Those who endorse the principle of instantiation are known as in re realists or "immanent realists".