If Quine is to avoid the problem of false existentials without exiting the theory of reference, he will need to resort to semantic ascent. Ontological commitment to a kind K must somehow involve the predicate ‘K’. That will allow ontological commitment to centaurs and ontological commitment to unicorns to be distinguished, even though ‘centaur’ and ‘unicorn’ are co-extensional. Indeed, Quine does suggest “withdrawing to a semantical plane” when the ontological commitments of the theory one is addressing outrun the ontological commitments of one's own theory. He writes, referring to the ontologically profligate philosopher McX: 