The Ontological Argument

Abstract

Ontological arguments are deductive arguments for the existence of God from general metaphysical principles and other assumptions about the nature or essence of God. There have been three very signifi cant developments in the history of ontological arguments. The fi rst is the ontological argument developed by St Anselm of Canterbury in the eleventh century. The second is the argument sketched by Descartes in the late seventeenth century and completed by Leibniz in the early eighteenth century. And the third development consists of the numerous ontological arguments of the twentieth century that explicitly utilize modal logic, particularly those of Malcolm, Hartshorne, Plantinga, and Godel. My chief aim in this chapter is to logically evaluate logical reconstructions of each of these six arguments. I shall also present and logically discuss two of my own explicitly modal ontological arguments. The logical evaluation of a logical reconstruction of an argument often requires that we explicitly identify assumptions that are only implicit in the author’s original presentation of the argument. And in some cases, it might involve the inclusion of “plausible” philosophical principles that are consistent with the author’s worldview, principles that strengthen the argument if we include them among the premises of the reconstruction. My modus operandi will be to make each of the arguments as strong as possible before critically evaluating them. Even though I shall try to remain reasonably faithful to the intent of the original author of each argument, my main objective will be logical instead of historical. A good deductive argument should be valid and have true premises. And if it is to be convincing it should not beg the question. Ontological arguments are frequently the target of parodies, perhaps more so than any other argument in philosophy. So in addition to checking the arguments we discuss for validity, truth, and question begging, I shall also test their vulnerability to being refuted by some of the well-known parodies in the philosophical literature. Like many other philosophical arguments of note, ontological arguments stand or fall on the acceptability of some very high-level and well-entrenched principles of metaphysics and logic. And, as we shall see, some ontological arguments are logically much stronger than what fi rst meets the eye.