- published: 18 Apr 2014
- views: 7858
Modal logic is a type of formal logic primarily developed in the 1960s that extends classical propositional and predicate logic to include operators expressing modality. Modals—words that express modalities—qualify a statement. For example, the statement "John is happy" might be qualified by saying that John is usually happy, in which case the term "usually" is functioning as a modal. The traditional alethic modalities, or modalities of truth, include possibility ("Possibly, p", "It is possible that p"), necessity ("Necessarily, p", "It is necessary that p"), and impossibility ("Impossibly, p", "It is impossible that p"). Other modalities that have been formalized in modal logic include temporal modalities, or modalities of time (notably, "It was the case that p", "It has always been that p", "It will be that p", "It will always be that p"),deontic modalities (notably, "It is obligatory that p", and "It is permissible that p"), epistemic modalities, or modalities of knowledge ("It is known that p") and doxastic modalities, or modalities of belief ("It is believed that p").
A explanation of the basics of Modal Logic, including the difference between the K, T, B, S4 and S5 systems of modal logic (100 Days of Logic).
A brief, intuitive introduction to the basic concepts of modal logic. The box & diamond operators, necessity & possibility, possible worlds, etc. If you're already familiar with all this stuff, you can skip this video. Part 2: http://www.youtube.com/watch?v=0djILNja3ZE
Max Cresswell lecture: "Arthur Prior - The History of Temporal and Modal Logic in the 1950s as seen from a Philosophical Perspective", Aalborg University, Denmark, May 16, 2008.
An introduction to the basic concepts of the system K in modal logic.
I briefly discuss the development of modern modal logic, to set the scene for Quine's attack.
An introduction to modal logic for my PHIL478P course.
The rules for truth trees in system K, and some advice about constructing trees in K. I then use trees to prove the validity of two simple arguments.
What are possible worlds? What does it mean to say something might have been true? Watch Part 1 of our discussion on David Lewis’ modal realism to find out! Part 2! http://tinyurl.com/pdxgkjt Metaphysics playlist: https://www.youtube.com/playlist?list=PLvoAL-KSZ32cX32PRBl1D4b4wr8DwhRQ4 Subscribe! http://tinyurl.com/pr99a46 Patreon: http://www.patreon.com/PhilosophyTube Facebook: https://www.facebook.com/PhilosophyTube Twitter: @PhilosophyTube Email: ollysphilosophychannel@gmail.com Google+: google.com/+thephilosophytube Suggested Reading: David Lewis, On The Plurality of Worlds Sponsors! Juho Laitalainen Eric Driussi Ethan Arnold Rich Clarke Total Philosophy Looking Glass Universe D.j. The University of St Andrews If you or your organisation would like to financially support Phil...
10 Modal Logic Puzzles for you to test your modal logic skills with. Including proofs of the various iterations of Axiom K, and the consequences of the Necessitation Rule and Axiom K (distributing and exporting necessity and possibility across implication, conjunction and disjunction).