On Fri, Sep 20, 2013 at 3:58 PM, Bruno Marchal <marc...@ulb.ac.be> wrote: > > On 19 Sep 2013, at 16:51, Telmo Menezes wrote: > >> On Thu, Sep 19, 2013 at 4:31 PM, Bruno Marchal <marc...@ulb.ac.be> wrote: >>> >>> >>> On 18 Sep 2013, at 21:45, Telmo Menezes wrote: >>> >>>> On Wed, Sep 18, 2013 at 6:13 PM, Bruno Marchal <marc...@ulb.ac.be> >>>> wrote: >>>>> >>>>> >>>>> >>>>> On 18 Sep 2013, at 11:43, Telmo Menezes wrote: >>>>> >>>>>> <snip> >>>>>> >>>>>> >>>>>> But maybe it doesn't. At least some week form of solipsism, where >>>>>> there is in fact only me, but the notion of "I" is extended. No? >>>>> >>>>> >>>>> >>>>> >>>>> I would say that there are as many notion of "I", that there are >>>>> intensional >>>>> nuances. >>>>> >>>>> The most basic is the 3-I, like when the machine says I have two arms, >>>>> (Bp), >>>>> then there is the 1-I, when the machine says that she has two arms, and >>>>> it >>>>> is the case that she has two arms (Bp & p), then there is the observer >>>>> I, >>>>> when the machine says that she has two arms, and it is possible, not >>>>> contradictory, for that machine that she has two arms, or equivalently >>>>> that >>>>> 0=0 is not a contradiction, Bp & Dp, >>>> >>>> >>>> >>>>> equivalent with Bp & Dt. Then the >>>>> "feeler" whioch combines both Dt and "& p". >>>> >>>> >>>> >>>> Bruno, I don't understand these last two lines. What's Dt? What's a >>>> feeler? >>> >>> >>> >>> A feeler is someone who feels. My automated spelling verifier does not >>> complain, but perhaps he get tired with me :) >> >> >> Ok. No, it's right. I just thought there was something more to it. > > > Nice! > > > > >> >>> D is for diamond. Dp, in modal logic, often written <>p is an >>> abbreviation >>> of ~B~p. >> >> >> I know, I meant Dt vs. Dp. Was it a typo? Otherwise what's Dt as opposed >> to Dp? > > > OK, sorry. "t" is for the logical constant true. In arithmetic you can > interpret it by "1=1". I use for the logical constant false. > > As the modal logic G has a Kripke semantics (it is a so-called normal modal > logic), The intensional nuance Bp & Dp is equivalent with Bp & Dt. "Dt" will > just means that there is an accessible world, and by Bp, p will be true in > that world.

Ok, thanks. If there is one or more accessible worlds, why not say []t? (I'm using [] for the necessity operator) Is there any conceivable world where D~t? If so, can't we say ~D~t and thus []t? Isn't the only situation where ~Dt the one where this is no world? > > > >> >>> For example (possible p) is the same as (not necessarily not p). Like "it >>> exists x such that p(x)" is the same as not for all x do e have not p(x). >>> >>> Bp & Dp, really means that p is true in all worlds (that I can access) >>> and >>> Dp really means that there is such a world (if not, classically Bp can be >>> vacuously true). Normally there will be some explanations of modal logic >>> (on >>> FOAR). Older explanations on this list exists also, may be by searching >>> on >>> "modal" (hmm... you will probably get too many posts ...). >> >> >> I've been slowly going through Chellas. > > > It is a very good book. Boolos 1979 (and 1993) sum up very well Modal Logic > too. > >> >> Thanks! > > > Welcome! > > > Bruno > > > > http://iridia.ulb.ac.be/~marchal/ > > > > -- > 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 everything-list+unsubscr...@googlegroups.com. > To post to this group, send email to everything-list@googlegroups.com. > Visit this group at http://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/groups/opt_out. -- 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 everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/groups/opt_out.