“I was born with such intellect that the main pleasure for me in research studies lay in forming my own opinion instead of listening to the ones of other people.” And he did form a lot of opinions! Quoting the list of his achievements may take ten minutes or more. Like other giants of the Renaissance, Descartes was a philosopher first of all, and only then a physicist and mathematician. Like Archimedes, who asked for a standing point, Descartes demanded matter and motion saying that he would compose the Universe out of them. His explanation of the rainbow sounded incomparable! It was Descartes who denoted unknown values with letters x, y and z, exactly as we do it today, taught us how to denote grades, etc. Quite a lot, isn’t it? However, we have not yet mentioned the rectangular coordinates that bear the name of Cartesian ones in honor of the scientist. They say that he invented them watching a fly crawling along the tiled wall. The scientist put the theory into practice at once – at the theater. There was no order at the theater at that time – no rows and no seats. Proud-hearted noblemen visited the theater armed with swords, each of them would stand on his right for taking a seat where he wanted to. The duels often resulted in homicide. King Louis XIII, sick and tired of watching how his liege people kill each other, turned to Descartes for advice, and the great scientist suggested assigning numbers to rows and seats. This is the system we have today.