Quine’s justly famous paper “On What There Is” introduced a criterion of ontological commitment which has been almost universally accepted by analytic philosophers ever since. In this paper I try to unpack some of the substantive and controversial philosophical commitments that are presupposed by this criterion. The aim is not to show that the criterion is incorrect, but merely that it is not as obvious as it is taken to be by many, and that we might have reasons to explore alternative ways of thinking about ontological commitments.