The question asks whether angels can be moved in a vacuum. Before deciding this, Ockham very sensibly says, we must first determine if a vacuum can exist. He says that it can. For imagine that God should annihilate or uncreate the Earth, while conserving everything in the heavens the way they are. Then there would be nothing where the Earth used to be, and then there would be a vacuum.
If you were to insist that natural laws would require an inrushing of stuff into the void in order to full and thus eliminate the vacuum, Ockham says that so long as this doesn't happen instantaneously (and motion never occurs instantaneously), there would be some period of time however short in which a vacuum was present.
So, given that there can be a vacuum, angels can move in it. There are some additional complications thrown into the question, of course, but they're not to thrilling. The next question is about the composition of the continuum and that should be more interesting.
