This short paper is not broken into sections. The structure shown here is my analysis. In the text, very roughly, plain text is description, italicised text is discussion.
Ordinary language is quite casual about ontology. So casual in fact, that the way we talk about things we believe to exist is not distinguishable from the ways in which we talk about things we definitely don't believe to exist, other than through a knowledge of the context of the discourse, or some prior knowledge of the subject matter.
This is best illustrated by considering how people discuss what goes on in worlds which are described in works of fiction. Imagine a conversation between two readers of "The Lord of the Rings". Of course they might talk about various aspects of the book or the literary style of the author. These kinds of conversation are not of interest at present. They might also talk about the world which is described by the book, the characters which inhabit this world, and their adventures in their world. In doing so the readers would feel free to use language in no way different to the language which they would use if this fictitious world invented by Tolkien were the real world which we all inhabit. If there is any language (perhaps the use of informal quantifiers such as "all", "every", "none") which might be supposed ordinarily to involve "ontological commitment" these can be used freely in the context of such a discussion without the participants ever being supposed to have contradicted their firm belief that their subject matters were entirely fictional.
This is the magic of ordinary language, and its sensitivity to context.
Coming a little closer to the technical languages with which Carnap was more often concerned, we see an analogous procedure in the use of the language of arithmetic. Whatever a mathematician's philosophical views about the ontological status of the natural numbers, he is free to use a language such as that of first order arithmetic, with its quantifiers, to talk about the facts of arithmetic. He is entitled so to do without thereby being deemed to have engaged in metaphysics. Even if he thought numbers were entirely fictitious this would be on a par with normal usage of natural languages. Equally legitimate is the case in which Carnap and I find ourselves. We do not consider natural numbers to be fictitious, and therefore do not consider an explicit philosophical claim that they exist to be false, we are rather uncertain about what such a philosophical claim means, and are therefore unwilling to assent either to the claim or its denial. This has no bearing upon the legitimacy of talk about natural numbers, in an appropriate context, and casts no doubt upon the truths which are demonstrable about them. It follows that such talk cannot properly be supposed to commit the speaker to the existence of natural numbers, any more than talk about Tolkien's characters (even involving bound variables) can always be taken as a denial that these characters are fictitious.
In talking of these phenomena of ordinary language we do not need the special terms which Carnap introduces primarily for use in relation to the adoption and use of formal languages. Instead of talking of a "framework" it is more appropriate to talk of a "context" in which some discussion is taking place. Instead of talking about "external existence questions", it is sufficient to talk of assumptions, presuppositions, or simply of context.
The essay was written not long after Quine's "Two Dogmas" and in response to Carnap's "Empiricism Semantics and Ontology" . A misunderstanding might have been more understandable if Quine's knowledge of Carnap were exclusively based on that paper, in which the presentation of the issue reflects Carnap's then concern with semantics rather than the much earlier misgivings about metaphysical ontology which were closer to the roots of his philosophy.
Carnap's position is perhaps made easier to misunderstand by his eagerness to give some kind of sense to the metaphysical ontology which he finds without content. The meaningful question which he puts in place of the metaphysics is the question of "acceptability" of a "linguistic framework".
Quine's essay for the most part can be read as his taking apart a less than ideal rendition of Carnap's ontological position, until we come close to the end. In conclusion Quine makes the connection with the analytic/synthetic distinction, argues that Carnap's internal/external distinction is just the same distinction and can be dismissed by the arguments in his two dogmas.
As I have suggested, there are two different interpretations which can be given to the internal/external distinction in Carnap, according to whether the external questions are interpreted as metaphysics or as pragmatics. Neither of these is even faintly like the analytic/synthetic distinction.
In Carnap, the internal questions may be either analytic or synthetic according to whether whether their truth is determined by the L-rules of the language in question. The external question, whether it be metaphysics or pragmatics, is neither analytic nor synthetic.
In one of my undergraduate philosophy essays "Ontology", which so far as I can see was written in ignorance of this essay, I argue that the internal/external distinction is not absolute (not that Carnap said it was) but that these quesions, for different linguistic frameworks, form a hierarchy. Quine makes a similar point in this essay (a couple of decades earlier).