 Collingwood’s discussion of the ontological argument in An Essay on Philosophical Method gave rise to a lively epistolary exchange with Ryle (the exchange is published in the 2005 edition of An Essay on Philosophical Method). The correspondence was triggered by the publication of an article in Mind by Ryle (1935) which attacked Collingwood’s sympathetic appraisal of the ontological proof on the grounds that there are no such things as propositions which are both necessary and existential, i.e., no such things as metaphysical propositions, like the one asserting the necessary existence of God. Collingwood replied to Ryle in a private letter by claiming that that there is a third kind of proposition, philosophical propositions, which feature philosophical concepts, propositions such as “Mind exists” or “Matter exists”. Such propositions are necessary but not merely hypothetical because the philosophical concepts whose existence they assert are necessarily instantiated in the judgements employed by the practitioners of a given science. “Mind exists” in so far as one explains actions by means of rationalisations, rather than nomological explanations; the concept of mind is embedded in the kind of judgement or inference that it makes possible. The main bone of contention in the correspondence between Ryle and Collingwood was therefore not the ontological argument in its traditional form, but whether or not philosophy has an autonomous domain of inquiry, i.e., whether there are distinctive philosophical concepts, (concepts which allow for complete extensional overlap). As we have seen Collingwood later revisited the claim that philosophy has an autonomous domain of inquiry in An Essay on Metaphysics, where he reformulated it by saying that philosophy is not an ontological but a logical enquiry into the presuppositions which govern thought.