page_title: Ontological argument
section_title: René Descartes
hierarchical_section_title: Ontological argument / Development / René Descartes
context_page_description: An ontological argument is a philosophical argument, made from an ontological basis, that is advanced in support of the existence of God. Such arguments tend to refer to the state of being or existing. More specifically, ontological arguments are commonly conceived a priori in regard to the organization of the universe, whereby, if such organizational structure is true, God must exist.
  The first ontological argument in Western Christian tradition was proposed by Saint Anselm of Canterbury in his 1078 work, Proslogion, in which he defines God as "a being than which no greater can be conceived," and argues that such being must exist in the mind, even in that of the person who denies the existence of God. From this, he suggests that if the greatest possible being exists in the mind, it must also exist in reality, because if it existed only in the mind, then an even greater being must be possible—one who exists both in mind and in reality. Therefore, this greatest possible being must exist in reality.
  Since its initial proposal, few philosophical ideas have generated as much interest and discussion as the ontological argument.
context_section_description: René Descartes (1596–1650) proposed a number of ontological arguments that differ from Anselm's formulation. Generally speaking, they are less formal arguments than they are natural intuition.
  In Meditation, Book V, Descartes wrote:
  But, if the mere fact that I can produce from my thought the idea of something entails that everything that I clearly and distinctly perceive to belong to that thing really does belong to it, is not this a possible basis for another argument to prove the existence of God?  Certainly, the idea of God, or a supremely perfect being, is one that I find within me just as surely as the idea of any shape or number.  And my understanding that it belongs to his nature that he always exists is no less clear and distinct than is the case when I prove of any shape or number that some property belongs to its nature.
  Descartes argues that God's existence can be deduced from his nature, just as geometric ideas can be deduced from the nature of shapes—he used the deduction of the sizes of angles in a triangle as an example. He suggested that the concept of God is that of a supremely perfect being, holding all perfections. He seems to have assumed that existence is a predicate of a perfection. Thus, if the notion of God did not include existence, it would not be supremely perfect, as it would be lacking a perfection. Consequently, the notion of a supremely perfect God who does not exist, Descartes argues, is unintelligible. Therefore, according to his nature, God must exist.
caption: French thinker René Descartes proposed several arguments that could be termed ontological.
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