Brandeis University, Philosophy Department
PHIL 1A
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Anselm's
Ontological
of Argument

Professor Andreas Teuber
Prof. Teuber

Anselm's Ontological Argument

1. G-d exists in the understanding.

2. G-d might have existed in reality (G-d is a possible being).

3. If something exists only in the understanding and might have existed in reality, then it might have been greater than it is.

From these three basic premises. Anselm believes, it follows that G-d exists in reality; i.e. if we accept (1) - (3), we are committed by the rules of logic that

4. If G-d is understood as "the being than which none greater is possible," G-d must necessarily exist not only in the understanding, but in reality as well."

Instead of showing, however, that the existence of G-d follows directly from steps (1) through (3), Anselm invites us to suppose that G-d does not exist and then he proceeds to show by a reductio ad absurdum argument that if we suppose as much, such a supposition combined with (1) through (3) will lead to an absurd and/or contradictory result. Since the supposition that G-d does not exist leads to an absurdity, it must be replaced by the conclusion that G-d does exist.

4'. Suppose G-d exists only in the understanding.

5. G-d might have been greater than He is.

Step (5) follows from steps (2), (4') and (3)

6. G-d is a being than which a greater is possbile.

If we accept steps (1) through (4'), we must accept (6), but (6) is unacceptable. (6) is the absurdity Anselm was after. By substituting "G-d" in (6) with "the being than which none greater is possible, we get

7. The being than which none greater is possible is a being than which a greater is possible.

If we accept that steps (1) through (3) are true, then we must reject (4') as false:

8. It is false that G-d exists only in the understanding.

And since step (1) tells us that G-d exists in the understanding, and (8) tells us that G-d does not exist only there, we can conclude that

9. G-d exists in reality as well as in the understanding.

 

 


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Last Modified: 03/26/08
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