Full Idea
The concept of motion is logically subsequent to that of occupying as place at a time, and also to that of change. Motion is the occupation, by one entity, of a continuous series of places at a continuous series of times.
Gist of Idea
Occupying a place and change are prior to motion, so motion is just occupying places at continuous times
Source
Bertrand Russell (The Principles of Mathematics [1903], §442)
Book Reference
Russell,Bertrand: 'Principles of Mathematics' [Routledge 1992], p.469
A Reaction
This is Russell's famous theory of motion, which came to be called the 'At-At' theory (at some place at some time). It seems to mathematically pin down motion all right, but seems a bit short on the poetry of the thing.
Related Idea
Idea 22747 A man walking backwards on a forwards-moving ship is moving in a fixed place [Sext.Empiricus]