I have read in several pages that Rudolf Carnap, just as David Lewis (The creator of Modal Realism philosophical hypothesis) proposed that every logical proposition exists as a universe

But is this right? Did Carnap propose some kind of Modal Realism?





  • The IEP entry on Modal Metaphysics states : "One of the first Ersatz views was Rudolf Carnap’s (1947) Sententialism, where maximally consistent sets of sentences took the place of possible worlds. Writing before Kripke, however, Carnap did not speak of these sets as “ersatze” for worlds. He just utilized the sets as they were, referring to them as “state descriptions.”".
    – nwr
    Jul 26, 2019 at 2:45
  • 1
    No, Carnap did not propose anything like modal realism. He was one of the early proponents of modal logic, but what he proposed can be more aptly called modal nominalism. To Carnap, necessity was analytic necessity, that is necessity imposed by conventions in what he called "linguistic frameworks". Instead of worlds he has consistent collections of sentences, state descriptions, and the only things true in all of them are those derivable from postulates and definitions of the framework. If he did use the language of worlds they'd be nothing more than linguistic fictions.
    – Conifold
    Jul 26, 2019 at 5:11


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