In this chapter I want to focus on something that I think lies at the heart of the Meditations, namely Descartes’ notion of externality or distinctness from the subject. This notion could also be understood as objectivity. It seems to me that irrespective of what other aims Descartes might have had in composing the Meditations, one was to get clear on what it is for a thing to be independent from a subject, and also how such independence is connected to external existence. It will be argued that true and immutable natures are a key to both of these aims. I argue that one of Descartes’ substantive achievements in the Meditations is his re-thinking of externality or objectivity, i.e., the question about the conditions for an idea to be directed toward an object. The chapter also considers Kant’s objection that any ontological argument is doomed to fail because existence is not a predicate.  I argue that Descartes denies that existence is a predicate and that this denial in fact constitutes the core of his ontological argument.