What are the types of modal logic?

Modal logic can be viewed broadly as the logic of different sorts of modalities, or modes of truth: alethic (“necessarily”), epistemic (“it is known that”), deontic (“it ought to be the case that”), or temporal (“it is always the case that”) among others.

What is modal logic used for?

Modal logic is a collection of formal systems originally developed and still widely used to represent statements about necessity and possibility. The basic unary (1-place) modal operators are most often interpreted “□” for “Necessarily” and “◇” for “Possibly”.

What are the basic features of modal logic?

modal logic, formal systems incorporating modalities such as necessity, possibility, impossibility, contingency, strict implication, and certain other closely related concepts.

What is S4 modal logic?

modal logic … to T is known as S4; that obtained by adding Mp ⊃ LMp to T is known as S5; and the addition of p ⊃ LMp to T gives the Brouwerian system (named for the Dutch mathematician L.E.J. Brouwer), here called B for short.

What is modal in philosophy?

Modal reasoning is central to human cognition, since it is pervasive both in philosophy and in every-day contexts. It involves investigating and evaluating claims about what is possible, impossible, essential, necessary, and contingent.

What is modal logic in AI?

Modal logic began as the study of different sorts of modalities, or modes of truth: alethic (“necessarily”), epistemic (“it is known that”), deontic (“it ought to be the case that”), temporal (“it has been the case that”), among others. The first goal is to introduce the basic techniques and concepts in modal logic.

What is quantified modal logic?

The Simplest Quantified Modal Logic (SQML) defines a class of first-order modal languages, a semantic theory for those languages, and a complete system of axioms and rules of inference for the semantics.

Is modal logic extensional?

Modal logic can be regarded also as the most simple appearance of such studies: it extends extensional logic just with a few sentential functors: these are intensional, and they are interpreted (in the metarules of semantics) as quantifying over possible worlds.

What is Modal very likely?

Modal verbs

meaning	which verb?	example
really certain	must	The cakes must be ready soon. They’ve been in the oven for an hour.
can’t	You can’t be hungry. You had a huge lunch.
very likely	should	The traffic isn’t heavy. We should be there in an hour.
ought to	The traffic isn’t heavy. We ought to be there in an hour.

What is the modal possible?

Modal verbs express if something is certain, probable or possible. If something is possible in the future, we use ‘could’, ‘might’ or ‘may’ before the main verb to talk about it. If something is possible now or was possible in the past we add the word ‘have’ after the modal verb. This still expresses possibility.