  Propositions 5–8 are all devoted to attractive force. In Proposition 5 Kant argues that matter must have an attractive force in order to fill space. Kant's argument is that if there were only repulsive forces, then matter “would disperse itself to infinity” (4:508) since neither space nor other matter could limit it. Proposition 6 argues that both attractive and repulsive forces must be considered essential to matter. That is, attractive forces alone are not sufficient to account for matter filling a space, since if matter consisted solely of attractive forces, there would be no force to counteract the attractive force being exercised and the universe would collapse into a single point. Together, Propositions 5 and 6 make up a ‘balancing argument’, which Kant had already used in the earlier Physical Monadology. (A balancing argument is an existence proof for a type of force. Its premises are (1) an accepted universal fact, viz.  that a certain stable configuration obtains; and (2) a type of force independently known to exist. The argument seeks to prove that the stability in question is impossible unless a second kind of force exists to balance the first kind. In Kant's particular version of the balancing argument, the universal fact is the constancy of mass density in a control volume; and the given force is “original repulsion,” whose existence he proves in Proposition 4.) Proposition 7 then specifies how attractive forces are to be understood, namely as the immediate action of matter on other matter through empty space (and therefore at a distance). Kant thus directly confronts the metaphysical question of how to understand attraction that Newton attempted to avoid by positing it merely mathematically. As Kant interprets the situation, Newton “abstracts from all hypotheses purporting to answer the question as to the cause of the universal attraction of matter … [since] this question is physical or metaphysical, but not mathematical” (4:515). In response to the “most common objection to immediate action at a distance,” namely “that a matter cannot act immediately where it is not” (4:513), Kant argues that action at a distance is no more problematic than action by contact (whether it be by collision or pressure), since in both cases a body is simply acting outside itself. Proposition 8 concludes by arguing that attractive forces act immediately to infinity and by adding a “preliminary suggestion” (4:518) as to how one might be able to construct the concept of cohesion (which Kant understands as attraction that is restricted to contact).