Ontological Arguments and Belief in God

This monograph represents a comprehensive philosophical critique of ontological arguments for God's existence. Oppy systematically examines the entire tradition of ontological argumentation, from Anselm's original formulation through contemporary modal versions, demonstrating that none succeed in providing rationally compelling grounds for theistic belief. The work stands as perhaps the most thorough analytical treatment of ontological arguments in recent philosophical literature.

Oppy's central thesis holds that ontological arguments fail to meet minimal standards of dialectical effectiveness. He argues that these arguments cannot rationally compel acceptance from those who do not already believe in God, since the premises required for their soundness invariably assume what they seek to prove. The analysis proceeds through meticulous examination of various formulations, including Anselmian perfect being arguments, Cartesian arguments from divine essence, and modern modal arguments developed by Hartshorne, Malcolm, and Plantinga.

The methodological approach combines formal logical analysis with careful attention to the dialectical context in which arguments function. Oppy distinguishes between different criteria for evaluating arguments: formal validity, soundness, persuasiveness, and what he terms "dialectical efficacy." While acknowledging that many ontological arguments achieve formal validity, he demonstrates that they uniformly fail the test of dialectical efficacy because they require premises that only theists would accept.

Particularly significant is Oppy's treatment of modal ontological arguments, which had gained considerable attention following Plantinga's reformulation. He shows that while these arguments may avoid some traditional objections, they still depend on question-begging modal intuitions about possible worlds containing maximal greatness. The work engages extensively with defenders of ontological arguments, including Plantinga, van Inwagen, and Leftow, offering detailed responses to their positions.

The monograph's contribution extends beyond mere criticism. Oppy develops a general theory of rational argument evaluation that has influenced subsequent debates in philosophy of religion. His emphasis on dialectical context has shifted discussion away from purely formal considerations toward questions about the social and epistemic functions of religious arguments. This work effectively ended the mid-twentieth century revival of ontological arguments, establishing new standards for assessing their philosophical viability. Contemporary discussions of ontological arguments invariably reference Oppy's critique, which remains the definitive skeptical treatment of this argumentative tradition.