Full Idea
Law 1: Every body perseveres in its state of being at rest or of moving uniformly straight forward, except insofar as it is compelled to change its state by forces impressed.
Gist of Idea
1: Bodies rest, or move in straight lines, unless acted on by forces
Source
Isaac Newton (Principia Mathematica [1687], Axioms)
Book Reference
Newton,Isaac: 'Philosophical Writings' [CUP 2004], p.70
A Reaction
This is the new concept of inertia, which revolutionises the picture. Motion itself, which was a profound puzzle for the Greeks, ceases to be a problem by being axiomatised. It is now acceleration which is the the problem.