You want to use your microscope to settle your differences. It will reveal a physical structure in cuttlefish tissue that is indiscernible to the naked eye, you say, yielding invaluable clues about the workings of the heart and other organs. “Futile,” responds Aristotle. It is not that physical structure has no role to play in bodily functions (although Aristotle does in fact deny that organic tissue has microscopic structure). It is rather that physical structure is not at all the right kind of thing to account for biological function. Even if it were to explain how a cuttlefish moves, it
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Aristotle might have a point here. The big misses, like the function of the brain or the circulation of blood, wouldn't have benefitted from a microscope, and would have benefitted from some systematic investigation of the purpose of various organs. We absolutely have ways to be empirical about the _telos_ of body systems and Aristotle knows about them.
