We do not live in vacuum chamber even if some of us own one.
Just because we don't live in a vacuum doesn't mean we can't think about it. Ah, but using Newton's Laws, we CAN live for some time in space or on the moon in a vacuum and we can have astronauts drop the feather and a hammer on the moon and do that experiment. And we can use TV cameras incorporating Einstein's work to beam it back to us on earth using an extrapolation of Hertz's discoveries. And we can videotape it and watch it over and over. In fact, here is a link to it:
http://nssdc.gsfc.nasa.gov/planetary/image/featherdrop_sound.mov"
Would Aristotle deny this could happen?
And, of course, we can jump out of planes and drop bricks. I recall a news item about two skydivers playing catch with a pumpkin that was lighter than they were. One of them missed. It went through the roof of some poor guy's house long before those heavier guys reached the ground. Would Aristotle deny this coulc happen?