Isaac Newton

Sir Isaac Newton FRS PRS (25 December 1642 – 20 March 1727) was an English mathematician, physicist, astronomer, theologian, and author (described in his own day as a "natural philosopher") who is widely recognised as one of the most influential scientists of all time, and a key figure in the scientific revolution. His observations laid the foundations of classical mechanics, optics, infinitesimal calculus, and other fields. Newton formulated the laws of motion and universal gravitation formed the dominant scientific viewpoint until they were superseded by Albert Einstein's theory of relativity. Newton used his mathematical description of gravity to define the laws of planetary motion and eradicate doubt about the Solar System's heliocentricity. He was president of the Royal Society from 1703 until his death, and was knighted in 1705.

The third item in Newton's Laws of Motion, written in Latin, is often translated as "For every action, there is an equal and opposite reaction."

Isaac Newton in The Case of the Toxic Spell Dump
Isaac Newton, an English thaumaturge, summarized the necessary balance of good and evil thusly: "For every quality, there is an equal and opposite counter-quality."