  Once we have formed this idea of that than which a greater cannot be thought, Anselm says, we can see that such a being has features that cannot belong to a possible but non-existent object – or, in other words, that (2) is true.  For example, a being that is capable of non-existence is less great than a being that exists necessarily. If that than which a greater cannot be thought does not exist, it is obviously capable of non-existence; and if it is capable of non-existence, then even if it were to exist, it would not be that than which a greater cannot be thought after all.  So if that than which a greater cannot be thought can be thought – that is, if it is a possible being – it actually exists.  (This reading of the argument of the Proslogion is developed at length in Visser and Williams 2008, chapter 5.)