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). > Against Symmetry: > > If we are counting empirical frequencies, then an A that is not a B > will lower the frequency of "As are Bs"; however, it will not alter > the frequency count for "Bs are As". Exactly. > What this highlights for me is the idea that NARS truth values attempt > to reflect the evidence so far, while probabilities attempt to reflect > the world. Well said. This is exactly the difference between an experience-grounded semantics and a model-theoretic semantics. Once again, the difference in truth-value functions is reduced to the difference in semantics, what is, what the "truth-value" attempts to measure. Pei > --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/?&; > Powered by Listbox: http://www.listbox.com > ------------------------------------------- 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
