I don't know if Euclid got it from somewhere else (worth checking), but arguably his major contribution to modern thought is rule-based reasoning, even more than his geometry. After all, much of the geometry needed for Newtonian physics is not in Euclid:as far as I know there's no idea of co-ordinates in Euclid, the geometry is all abstract; rather, it's the way he constructs his system from axioms and rules that is important (as well as the basis he gives to both more abstract and more concrete later geometries).

12th June 2008, original idea late '07