 What we see here is that Descartes, despite holding motion to be the motion of bodies relative to one another, also held there to be a privileged sense of motion; in a terminology sometimes employed by writers of the period (see Rynasiewicz 2019, §3), he held there to be a sense of ‘true motion’, over and above the merely relative motions. In logical terms we can make the point this way: while moves-relative-to is a two-place predicate, moves-properly-speaking is a one-place predicate. (And this, even though it is defined in terms of relative motion: let contiguous-surroundings be a function from bodies to their contiguous surroundings, then x moves-properly-speaking is defined as x moves-relative-to-contiguous-surroundings(x).)