> Consider the following line of reasoning. Let p be the proposition > "Ronald was born in New York." From p, we can infer q: Ronald was born > in the United States. From q, we can infer r: It is possible that > Ronald was born in New Jersey. On the other hand, from p we can infer > s: It is not possible that Ronald was born in New Jersey. We have > arrived at a contradiction. What is wrong? Note: To answer the > question, familiarity with modal logic is not needed.
Lotfi, you're confusing "logical consequence" with "consistency". It's true that q is a logical consequence of p; it's not true that r is a logical consequence of q. There's no logical system that I'm familiar with in which you can *infer* r from q. It is true that r is *consistent with* q, but that doesn't mean you can infer r from q. You don't need modal logic to see the problem. From p&q you can infer p; p is consistent with ~q; but p&q is inconsistent with ~q. This example is isomorphic to yours. -- Joe _______________________________________________ uai mailing list uai@ENGR.ORST.EDU https://secure.engr.oregonstate.edu/mailman/listinfo/uai
