Thanks for making these videos! They're are easier to understand than every other resource on modal logic I've found. There is one thing I don't get about the semantics of quantifier operators though. The way I understand the existential operator is as referring to existence in a platonic sense, like when we one says "for every prime there exists a larger prime". It seems to me like a weird choice of semantics to understand existence as physical existence. It also seems to make the system less expressive, because there is no way to express existence in every possible world, while the converse is true: if existence means existence in every possible world, I can always define a function F(w, x) as true if x physically exists in world w, and then instead of saying "∀x P, w" I can say "∀x F(w, x) → P, w". This would also make the paradox you mention not a paradox anymore since whenever something exists, it would exist in every possible world, which is what one would expect of abstract entities like numbers. So why is it that the existential quantifier is understood as ranging over the set of things that exist in the one possible world only, and are there any alternative interpretations I could look into? Thanks!

Amazing video! I've never seen this problem explained so simply and elegantly. A great resource!

The thin concept of existence may handle the 'non-actual' well, but how does it account for the genuinely substantive - i.e. the notion of 'things' from which everything is composed? Granted, in modern physics, there is a case for only relations and not actual bits of stuff . But how, under the 'thin' account, do we capture, logically, the notion of absolute things? I guess we just kind of posit them? Maybe as a general case or a theory or special modifier? - anyway, this is all fascinating stuff!

Hi! Loving the videos, thanks so much for making them :) Was curious whether you'll do one on two-dimensional semantics and issues surrounding it?

Any chance you’d consider making a video about Free Logic? May be a useful complement to this and related videos?

Thank you so much for making this kind of videos. I find the idea of thick and thin existence really interesting. Are there any books, articles or works of particular philosophers that I can read further if I want to dig deeper on this idea? Thanks a lot!

Thin existence: conceptual Thick existence: realized Please help, I know nothing.

The ironic thing about this is that the whole system of symbolic logic and it's ideas don't really even exist in the sense that the material world does. If Pegasus can't be understood to exist at least in some symbolic sense, then why should any character of the language of logic?

Thank you, Dr Jago! Is this view related to the view you developed in your impossible worlds book?

Hi Attic, I've already mastered basic logic and reason (truth tables, fallacies) and I've taken a class in symbolic logic as well, and I feel comfortable with that too. What are the next steps (topics) in learning logic?

How do you model haptia as a nexus of perspectives, a model of models? I'm not saying she didn't physically exist, but that the way her meaning exists as a summed up being (rather than as separate atoms or whatever) is all mitigated through perception. What role does that play in structural logic?