Hume on the Idea of a Vacuum

Hume had two principal arguments for denying that we can have an idea of a vacuum, an argument from the non-entity of unqualified points and an argument from the impossibility of forming abstract ideas of manners of disposition. He also made two serious concessions to the opposed view that we can indeed form ideas of vacua, namely, that bodies that have nothing sensible disposed between them may permit the interposition of other bodies without any apparent motion or occlusion and that it is possible to conceive the contents of a room to be evacuated without being compelled to conceive the walls moving into contact. To reconcile these concessions with his arguments and show why we only “falsely imagine” that we can form the idea of a vacuum (T 1.2.5.14; SBN 58), Hume developed a psychological theory of the perception of “invisible and intangible distance” that has something in common with Berkeley’s account of the perception of outward distance. This paper argues that this theory is both untenable and inconsistent with fundamental Humean principles. It explains why Hume should have rejected the two arguments against the idea of a vacuum and why accepting ideas of vacua would have been more in line with the rest of his thought than attempting to deny that we have any such ideas.