[PHI 3000] Defining in/out of existence

One of the usual complaints against ontological arguments for the existence of God is that "you cannot define something into existence." Ontological arguments usually go something like this:

1. By definition, God is a perfect being.
2. If God didn't exist, then God wouldn't be perfect. 
3. (Therefore) God exists.

The objection, then, is that by defining God as "a perfect being," one has defined God into existence. Many, starting with Gaunilo, find this move suspect, since one can then define into existence the perfect island, the perfect dragon, and so on.

Now, is the converse move, namely, defining out of existence, equally suspect?

For instance, Herman Cappelen has argued that intuitions do not play an evidential role in philosophical arguments. His strategy is to define intuition in such a way that the term turns out not to refer to what any philosopher actually says or does.

Cappelen defines “intuition” as a proposition that is supposed to be foundational in the same way that perceptual propositions are thought to be foundational. Then he argues that, when philosophers talk about intuitions, they are not talking about foundational propositions that cannot be defeated by further evidence and arguments.

Can Cappelen define intuitions in philosophy out of existence? Or is this move as suspect as defining something into existence?