Full Idea
Some people would hold that two moments of time, or two points of space, imply each other's existence; yet the relation between these cannot be said to be causal.
Gist of Idea
Moments and points seem to imply other moments and points, but don't cause them
Source
Bertrand Russell (The Principles of Mathematics [1903], §449)
Book Reference
Russell,Bertrand: 'Principles of Mathematics' [Routledge 1992], p.476
A Reaction
Famously, Russell utterly rejected causation a few years after this. The example seems clearer if you say that two points or moments can imply at least one point or instant between them, without causing them.