In Bearing False Witness, Stark credits William of Ockham with recognizing "that space was a frictionless vacuum."
I had never heard this claim before, so I was prompted to investigate. This book seems to claim the exact opposite: a vacuum would be "a mathematical body of three dimensions that bodies can occupy for a time and then leave for other bodies to occupy. In [Ockham's] view, as in Aristotle's, there is no empty space of this sort" (446).
Well, I need my copy of Atomism and Its Critics. Once I get that, I'm sure I'll have this sorted. But if anyone has any insight on this point, let me know.