Term used by Aristotle for the theory of motion that denies that there is a void, and denies the existence of any force except impulsion. The idea is to eliminate mysterious ‘attractions’ from nature. In nature there can be ‘pushes’ but no ‘pulls’. The flight of projectiles, magnetic attraction, and the suction of fluids are among the phenomena the theory must explain. The view goes back to Empedocles, and is adopted by Plato in the Timaeus. In the 17th century the term became used more for the equally Aristotelian doctrine that contrary qualities ‘repel’, tending both to intensify one another, and to flee from one another. The common example is heat and cold, but Boyle mentions the theory that water forms spherical drops because as wetness flees from dryness it attempts to squeeze into the smallest possible surface area. See also action at a distance, field.