In his work Physics, one of the topics treated by Aristotle is about how the study carried out by mathematicians differs from that carried out by physicists. Considerations about mathematics being the language of nature can be found in the ideas of the Pythagoreans : the convictions that "Numbers rule the world" and "All is number", and two millennia later were also expressed by Galileo Galilei : "The book of nature is written in the language of mathematics".