In Aristotle's book "The Physics", Aristotle divided το "παν" (everything) into three roughly analogous elements: "matter" (the stuff of which the Universe is made), "form" (the arrangement of that matter in space) and "change" (how matter is created, destroyed or altered in its properties, and similarly, how form is altered). Physical laws were the rules governing the properties of matter, form and their changes. Later philosophers such as Lucretius, Averroes, Avicenna and Baruch Spinoza altered or refined these divisions. For example, Averroes and Spinoza have "active" principles governing the Universe which act on "passive" elements.