logic
Hi Loren
Nice questions.
2. Is quantum logic experienced on the microscopic level because it yields more truths there than classical logic does - a sort of logical correspondence principle?
Are you sure this is how you want to phrase this question? Are you a microscopic observer? Anyway, never mind. It is a good observation to note that quantum logic involves more 'truth values' than classical (which of course has only two). This may be viewed as a consequence of the linearity of the lattice of subspaces of a Hilbert space. Whereas logical OR for sets is
simply union, in the linear case it must be the smallest subspace containing a and b. This destroys distributivity, and it is a simple fact of lattice theory that a quantum lattice can only be Boolean if it is distributive.
3. We normally consider macroscopic observers to follow Boolean logic. How does such a classical observer perceive quantum, non-Boolean, events when measuring their properties?
Tricky! I'd like to see someone answer this properly. Look at:
Topos Theoretical Reference Frames on the Category of Quantum Observables
Elias Zafiris
http://arxiv.org/abs/quant-ph/0202057
4. Since the cosmos evolved from a predominantly quantum mechanical entity near the big bang to one more of classical logic today, has its overall logical system changed?
Why are you imposing a classical spacetime on a question about quantum logic? I don't understand why people do this. Our best understanding of quantum logic fits into a unified framework (via category theory) and the classical (gravitationally speaking) limit is to be viewed as a restricted domain within this formalism. The classical limit is complex. So, no one can answer your question at present.
One of the founders of topos logic, F.W. Lawvere, has written a lot on things like the topos of evolving sets which one can think of as encompassing 'stages of knowledge'. F. Markopoulou of Perimeter has written papers on this topos in the context of causal sets.
By the way, I have said a little about these matters elsewhere on PF, where you might find some interesting references.
Regards Kea