Thank you for the above, for my diary! On 24 March 2014 20:14, Bruno Marchal <[email protected]> wrote: > > New exercise: > > show > > (W,R) respects A -> []<>A > iff > R is symmetrical. >
OK, symmetrical means for all a and b, a R b implies b R a. A -> []<>A can (I hope) be read as "the truth of A in one particular world (which I will call this world) implies that for all worlds accessible from this world, there exists at least one world in which A is true". Well, there is indeed one world accessible from those other worlds, in which A is true - this one! Because all worlds accessible from this one can access this world (due to symmetry) and in this world A is true. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
