I'm very short on time because of jury duty, but a few remarks on
Andrew's comments:
1) It is very important to distinguish between postulating long-period
equilibrium and stationary technology in a mathematical model and
postulating it as a feature of the real capitalist economy. The
theoretical investigations postulate it in a model, and most writers are
careful to point out the fact that these assumptions do not apply in a
real capitalist economy with constant technical change.
2) I find Andrew's language rather confusing on the question of what
exactly is being proved. You can "prove" that someone (say Sraffa) has
made a logical error in deriving theorems from clearly stated modeling
assumptions (but I actually don't think this is true for Sraffa). You can
bring evidence to bear that a given model doesn't represent a given
phenomenon very well. Is the argument over the logic or over which model
represents capitalist reality better?
Duncan