Thinking about a necessary being › The argument of chapter II

A reconstruction of the argument can separate its main commitments:

1. A hearer understands the description of a being than which no greater can be conceived.
2. What is understood is in the understanding, in the sense just explained.
3. Suppose that the being described exists only in the understanding.
4. It could then be conceived as existing in reality, which Anselm treats as greater.
5. The supposed unsurpassable being would therefore be surpassable in thought.
6. Anselm rejects that contradiction and concludes that the being exists in reality as well.

This is a reconstruction, rather than a quotation. It makes visible the dependence of the conclusion on the comparison in the fourth step. The first two steps alone do not establish that an object exists outside thought. A critic can grant those steps and still question the later comparison or its use.

The method is a reduction to contradiction. It temporarily accepts the denial to show that it conflicts with another accepted commitment. Such reasoning is familiar outside theology: if an assumption entails incompatible conclusions, there is reason to reject it. The dispute here concerns whether Anselm has established the incompatibility without already assuming what he wants to prove.

One way to state the challenge is to distinguish the content of a description from whether anything satisfies it. If a description requires a certain feature, we can say that any actual instance must have that feature. It does not follow merely from that conditional statement that there is an instance. Anselm's argument needs its unsurpassability comparison to do more than restate a requirement.

Another question concerns the comparison itself. In what sense is an existing being greater than a merely conceived being? If the comparison concerns two actual beings, the denial has already been abandoned. If it concerns two descriptions, the critic can ask how comparing descriptions establishes a real object. These are local questions about the inference, not a general rule that reason can never establish existence.