The instantiation principle or principle of instantiation or principle of exemplification is the concept in metaphysics and logic (first put forward by David Malet Armstrong) 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. Those who endorse the principle of instantiation are known as in re (in thing or in reality) realists or 'immanent realists'.