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Carnap, Quine, and the return of metaphysics

I've been trying to understand why metaphysics made a comeback in the second half of the 20th century, and have a couple questions in relation to that. My basic understanding is that Quine made the case that we could make a principled decision between ways of speaking that make all the same predictions...whereas Carnap thought such a decision could only be made on the basis of specific use cases. If this is right -- and I'm not sure it is -- it's unclear to me why people take Quine to have successfully taken on logical positivism. Specifically, I'm confused by a number of points regarding "Two Dogmas of Empiricism," which attempts to reject positivism's analytic / synthetic distinction, as well as their foundationalism / reductionism.

First, why does logical positivism need the analytic / synthetic distinction? And does the failure of this distinction in particular have any consequences for the status of metaphysics?

Second, does Quine's anti-foundationalism have any consequences for the status of metaphysics?

Thanks for answering, and I appreciate the notice if I got anything wrong in laying these questions.
gpt
> why does logical positivism need the analytic / synthetic distinction?

I think it's helpful to follow the language of Carnap's *Empiricism, Sematics, and Ontology* and note a distinction not just between logical and empirical questions, but also between either and practical questions.

Carnap relies on these distinctions because they are what underpin his distinction between science and metaphysics. Science is what resolves logical and empirical questions, while metaphysics is what resolves practical questions.

Conversely, if we deny that we can make any clear distinction between these kinds of questions, then we deny that we can make any clear distinction between science and metaphysics--at least as Carnap construes them.

So Carnap needs this distinction between kinds of questions in order to underpin his distinction between science and metaphysics.

> does Quine's anti-foundationalism have any consequences for the status of metaphysics?

Quine denies our ability to make clear distinctions between these kinds of questions, and, accordingly our ability to make a clear distinction, like the one Carnap makes, between science and metaphysics.

The slogan that Carnap killed metaphysics and then Quine brought it back is rather an oversimplification. They had very different views about what metaphysics is--in some ways, Carnap's is more continuous with traditional views about metaphysics than Quine's is, so there's something unsatisfactory with this slogan.

For Carnap, the upshot is that, consistent with the tradition through Leibniz and Kant, metaphysics constitutes a distinct field which provides a foundation for the sciences. But, following the radicalization of Kantian agnosticism which takes shape especially in Dilthey and Nietzsche, his major sources for this, he denies that metaphysical questions are answerable on strictly rational grounds, and construes our answers to metaphysical questions to be an expression of our life-feeling--responsive to things like our constitution, our socioeconomic class, our place in cultural history, etc.

For Quine, we get rather the opposite situation. The downshot is that the traditional distinction of metaphysics as a distinct field is undermined. But the upshot is that metaphysics, no longer clearly distinguishable from science, can be addressed on rational grounds just as much as science can--as indeed, they're not clearly distinguishable.

So Quine rejects the traditional view of metaphysics as a foundation of science, but does so in a way that undermines Carnap's non-cognitivism about metaphysics.