of a body from the body itself). Though such distinctions are strictly impossible, Hume argues, we achieve the same effect by noting the various points of resemblance between different objects. Part 2: Of the ideas of space and time Hume's "system concerning space and time" features two main doctrines: the finitist doctrine that space and time are not infinitely divisible, and the relationist doctrine that space and time cannot be conceived apart from objects. Hume begins by arguing that, since "the capacity of the mind is limited", our imagination and senses must eventually reach a minimum: ideas and impressions so minute as to be indivisible. And since nothing can be more minute, our indivisible ideas are "adequate representations of the most minute parts of [spatial] extension". Upon consideration of these "clear ideas", Hume presents a few arguments to demonstrate that space and time are not infinitely divisible, but are instead composed of indivisible points. On his account, the idea of space is abstracted from our sense experience (arrangements of coloured or tangible points), and the idea of time from the changing succession of our own perceptions. And this means that space and time cannot be conceived on their own, apart from objects arranged in space or changing across time. Thus we have no idea of absolute space and time, so that vacuums and time without change are ruled out. Hume then defends his two doctrines against objections. In defending his finitism against mathematical objections, he argues that the definitions of geometry actually support his account. He then argues that since important geometric ideas (equality, straightness, flatness) do not have any precise and workable standard beyond common observation, corrective measurements, and the "imaginary" standards we are naturally prone to fabricate, it follows that the extremely subtle geometric demonstrations of infinite divisibility cannot be trusted. Next, Hume defends his relationist doctrine, critically examining the alleged idea of a vacuum. No such idea can be derived from our experience of darkness or motion (alone or accompanied by visible or tangible objects), but it is indeed this experience that explains why we mistakenly think we have the idea: according to Hume, we confuse the idea of two distant objects separated by other visible or tangible objects with the very similar idea of two objects separated by an invisible and intangible distance. With this diagnosis in hand, he replies to three objections from the vacuist