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Jonathan, thank you for an enjoyable and enlightening read. I'd like to take your provocative opening sentence seriously and see where it leads. If we had to formalize the operations of arithmetic for Roman numerals, we might develop a set of rules and conditions for letter incrementing/decrementing, substitution, and so on. Even something as basic as multiplication might be so onerous it could only be feasibly done by machine. Then algebra and higher-order functions are needed, and the sets of rules and conditions become still more astronomically complex. To say nothing of what would be required when we need calculus, diff eq's, complex numbers, and so on. We wouldn't even be able to solve for X, because X is already taken by a number! (That's an attempt at humor.) In our bizarro-Roman world, we'd recognize that the math required to calculate the trajectory of a cannonball actually does work, and we might therefore be tempted to say that this math describes how the world functions, that the rules and conditions we've discovered dictate how the particles of the universe behave -- although in reality, calculations with Arabic or binary numerals would be equally effective, only much simpler.
Perhaps we're in a version of this Roman mathematical nightmare today. In our world, there could be a completely undiscovered mathematics that is equally effective at doing for us what higher algebras can do, only in a simpler and more holistic or fundamental manner. In other words the complexity of our higher maths might emerge from the lower maths, in the same way that the vast complexity of the rules and conditions for solving a Roman-numerals differential equation would emerge from the rules and conditions for doing arithmetic in that system. I don't believe we're in a position yet to rule that out.
Of course no one knows what this ultimate fundamental mathematics might be. But the higher maths remind me of the pre-Copernican epicycles, which were useful for human calculations even though they are demonstrably not features of nature. The added entities of our higher maths may only *seem* necessary for our calculations because we don't have the tools to perform the same operations any other way. Applying Occam's razor, we should demand evidence that these maths really are features of the world (and not just useful/predictive to humans), evidence that is commensurate with their complexity, while at the same time looking for a fundamental mathematics. A deeper math could make our higher maths not only unnecessary, it may also lead to discoveries about the evolution mechanisms of life/intentionality/consciousness and so on -- in the way that Copernicus' model led to discoveries about gravitation, which might have been impossible had we insisted on sticking with the Ptolemaic system.
Thanks again for the stimulating essay -- I wish I'd had the opportunity to think about these questions for the Trick or Truth contest, which I sat out. Best of luck!
Karl Coryat