On Sat, Oct 11, 2008 at 5:38 PM, Pei Wang <[EMAIL PROTECTED]> wrote: > On Sat, Oct 11, 2008 at 4:10 PM, Abram Demski <[EMAIL PROTECTED]> wrote: >> Pei, Ben, >> >> I am going to try to spell out an arguments for each side (arguing for >> symmetry, then for asymmetry). >> >> For Symmetry: >> >> Suppose we get negative evidence for "As are Bs", such that we are >> tempted to say "no As are Bs". We then consider the statement "Bs are >> As", with no other info. We think, "If we found a B that was an A, >> then we would also have found an A that was a B; I don't think any >> exist; so, I don't think there are any Bs that are As." Thus, evidence >> against "As are Bs" is also evidence against "Bs are As". > > I see your point --- it comes from the fact that "As are Bs" and "Bs > are As" have the same positive evidence (both in NARS and in PLN), > plus the additional assumption that "no positive evidence means > negative evidence". Here the problem is in the additional assumption. > Indeed it is assumed both in traditional logic and probability theory > that "everything matters for every statement" (as revealed by Hempel's > Paradox).
Hmm... other additional assumptions will do the job here as well, and I don't see why you mentioned the one you did. An assumption closer to the argument I gave would be "The more negative evidence we've ween, the less positive evidence we should expect". --Abram ------------------------------------------- agi Archives: https://www.listbox.com/member/archive/303/=now RSS Feed: https://www.listbox.com/member/archive/rss/303/ Modify Your Subscription: https://www.listbox.com/member/?member_id=8660244&id_secret=114414975-3c8e69 Powered by Listbox: http://www.listbox.com
