Law 3: To any action there is always an opposite and equal reaction; in other words, the actions of two bodies upon each other are always equal and always opposite in direction.

(Newton 1999: 417)

the reports by Huygens, Wren, and Wallis, which were printed in the Philosophical Transactions of the Royal Society in 1668-1669. Huygens’s and Wren’s accounts deal with perfectly elastic collisions, Wallis’s deals with perfectly inelastic collisions. Huygens, Wren, and Wallis do not provide details of experiments or any account for deviations from the ideal. Newton provides details of experiments and an account of how to extend the ideal theory to nonideal cases. He makes the law empirical rather than a priori. Though the experiments are complex and inexact they afford empirical support for the equality of action and reaction in collisions.