Stathis Papaioannou wrote: > Brent Meeker writes: > > >>>Empirical science is universe-specific: eg., any culture, no matter how >>>bizarre its psychology compared to ours, would work out that sodium >>>reacts exothermically with water in a universe similar to our own, but >>>not in a universe where physical laws and fundamental constants are >>>very different from what we are familiar with. >>> >>>Mathematical and logical truths, on the other hand, are true in all possible >>>worlds. >> >>But this is really ciruclar because we define "possible" in terms of obeying >>our >>rules of logic and reason. I don't say we're wrong to do so - it's the best >>we >>can do. But it doesn't prove anything. I think the concept of logic, >>mathematics, and truth are all in our head and only consequently in the world. > > > Isn't this like saying that a physical object must be perceived iin order to > exist? We define physical phenomena in terms of the effect they have on our > senses or scientific instruments, but we assume that they are still "there" > when > they are not being observed.

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I don't see the analogy with defining "possible worlds" as those obeying some logic and then saying that logic is a prior or analytic because it obtains in all possible worlds. I agree that "logically possible" is broader than what we think is "nomologically possible". > > >>>The lack of contingency on cultural, psychological or physical >>>factors makes these truths fundamentally different; whether you call >>>them perfect, analytic or necessary truths is a matter of taste. >> >>If you directly perceived Hilbert space vectors, which QM tells us describe >>the >>world, would you count different objects? I think these truths are >>contingent >>on how we see the world. I think there's a good argument that any being that >>is >>both intelligent and evolved will have the same mathematics - that's the jist >>of >>Cooper's book. > > > If we lived in a world where whenever two objects were put together, a third > one > magically appeared, would that mean that > > (a) 1+1=3, because we would think that 1+1=3 > (b) 1+1=2, but we would mistakenly think 1+1=3 I say (a), but someone might still invent Peano arithmetic in which 1+1=2. It would be called "non-standard" arithmetic and only a few, ill regarded mathematicians would study it. :-) Brent Meeker --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~----------~----~----~----~------~----~------~--~---