Full Idea
There is no absolute state of rest; only relative motions are unambiguous. Contrast this with acceleration, however, which has the same magnitude in all inertial frames.
Gist of Idea
All motions are relative and ambiguous, but acceleration is the same in all inertial frames
Source
Frank Close (Theories of Everything [2017], 3 'Newton's')
Book Reference
Close,Frank: 'Theories of Everything' [Profile Books 2017], p.21
A Reaction
It seems important to remember this, before we start trumpeting about the whole of physics being relative. ....But see Idea 20634!
Related Ideas
Idea 20634 General Relativity says there is no absolute force or acceleration [Einstein, by Close]
Idea 21146 Electrons move fast, so are subject to special relativity [New Sci.]