Ontological Argument - Classification

Classification

The traditional definition of an ontological argument was given by Immanuel Kant. He contrasted the ontological argument (literally any argument "concerned with being") with the cosmological and physio-theoretical arguments. According to the Kantian view, ontological arguments are those which are founded on a priori reasoning.

Graham Oppy, who elsewhere expressed the view that he "see no urgent reason" to depart from the traditional definition, defined ontological arguments as those that begin with "nothing but analytic, a priori and necessary premises" and conclude that God exists. Oppy admitted, however, that not all of the "traditional characteristics" of an ontological argument (analyticity, necessity, and a priority) are found in all ontological arguments and, in his 2007 work Ontological Arguments and Belief in God, suggested that a better definition of an ontological argument would employ only considerations "entirely internal to the theistic worldview".

Oppy subclassified ontological arguments into definitional, conceptual (or hyperintensional), modal, Meinongian, experiential, mereological, higher-order, or Hegelian categories, based on the qualities of their premises. He defined these qualities as follows: definitional arguments invoke definitions; conceptual arguments invoke "the possession of certain kinds of ideas or concepts"; modal arguments consider possibilities; Meinongian arguments assert "a distinction between different categories of existence"; experiential arguments employ the idea that God exists solely to those who have had experience of him; and Hegelian arguments are from Hegel. He later categorized mereological as arguments that "draw on… the theory of the whole-part relation".

William Lane Craig criticised Oppy's study as too vague for useful classification. Craig argued that an argument can be classified as ontological if it attempts to deduce the existence of God, along with other necessary truths, from his definition. He suggested that proponents of ontological arguments would claim that, if one fully understood the concept of God, one must accept his existence. William L. Rowe defined ontological arguments as those that start from the definition of God and, using only a priori principles, conclude with God's existence.