section_path: History of the concept/Momentum/Isaac Newton
section_name: Isaac Newton
paragraph_text: Isaac Newton
  
  In 1687, Isaac Newton, in Philosophiæ Naturalis Principia Mathematica, just like Wallis, showed a similar casting around for words to use for the mathematical momentum. His Definition II defines quantitas motus, "quantity of motion", as "arising from the velocity and quantity of matter conjointly", which identifies it as momentum. Thus when in Law II he refers to mutatio motus, "change of motion", being proportional to the force impressed, he is generally taken to mean momentum and not motion.