Yeah, he was definitely arguing against atomism. Still interesting to speculate around it. And while he didn’t have to deal with some of the scientific discoveries, we certainly have to.
Would Aristotle have been surprised by modern science? Would that have in any way change his argument? Or is he still mostly concerned with what is “naturally” perceived only ?
Excellent questions. Anyone else? Aristotle did have experience of things he did regard as being in “perpetual motion,” namely the movements of the heavens; but this was at the macro level and closely associated in the ancient mind with the power of the gods (the “heavenly host”). I’m inclined to think that if he knew that there was similar perpetual movement on the very small scale, he would have been highly interested, and it would have resulted in some changes to his system. Whether it would have changed the details of his arguments seems likely–but which arguments, and how? That is a harder question, and for that we’d have to look into the details of individual arguments. It is very clear that he is not just concerned with what appears to our senses, because infinite divisibility plays a very important role in his analysis of space and time.
An awful lot of modern scientific discoveries were pretty shocking to the discoverers. I think it’s pretty safe to say Aristotle would be quite surprised to find out the speed of light is constant, and I’m sure he’d find quantum theories just as baffling as the rest of us. But those don’t really come into play unless you’re dealing with things that are incredibly fast or incredibly small, so I’m not sure how much he would alter his ideas for them.
As far as things, that would force him to reevaluate, I think you’re right to mention inertia. He is operating under the assumption that if a thing is moving, something must be actively moving it. Newton’s first law invalidates a lot of Aristotle’s premises, but I don’t think it destroys the argument completely. Objects moving purely under inertia would only move at a constant speed in a perfectly straight line. Changes in speed and direction do need to be caused by outside forces.
Of course, that brings us to the other big piece of the celestial motion puzzle he’s missing: universal gravitation. He understood that heavy (dense) objects tend to sink and that light ones tend to rise, but he had no idea that all material objects exert a gravitational pull, and that it’s gravity and inertia working in tandem that cause the motions of the heavenly bodies. Newtonian mechanics would force Aristotle revise his physics (in the modern sense of the word), but I don’t know that he’d have to completely abandon his metaphysics. We don’t really know, after all, what gravity actually is; we just know what it does. There’s no scientific test you can run to prove that the fundamental forces aren’t the workings of gods.
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