We had some fun discussion at Canterbury last Friday on the question of 'what is existence?'. Philip generously recommended this blog when he introduced me, so I should probably direct any new visitors to the post on which my talk was based: here. Other related posts may be found under the 'metaphysics' category on the left sidebar. (Comments and counterarguments welcome, as always!)
Update: My central argument could be summarized as follows:
1. Ordinary existence claims (e.g. denying that the tooth fairy exists) serve to distinguish between rival possible worlds, whereas ontological disputes instead concern how best to describe a (qualitatively) given world.
2. Substantive inquiry into the nature of the world requires narrowing the possibilities, with the ultimate aim being to discern which possibility has been actualized. (This is arguably the job of empirical science.)
3. So, ontology is lacking in worldly 'substance'.
Meta-ontological projectivism: My positive view is then that ontology (and the rest of philosophy, for that matter) is better understood as a rational construction: it concerns the question of how to carve up the world - or project our concepts onto it - most coherently. The ultimate end (truth) is fixed by the ideals of rationality, rather than any thing in the world. The proposed meta-philosophy in this sense privileges the epistemic over the ontic.