If we go back to school times and think of the "trouble kid", the friend who gets us into trouble, the one who complicates everything, we could think of René Descartes in this way! Until his works, the world of philosophy was guided by natural thinking: we can think about the things we see and trust our thoughts. Philosophy passed from the object that appeared to the subject that thought it. After Descartes there is a great turning point, because after him we cannot naturally trust our mind, we have to put everything in brackets, doubt everything and we are the builders of reality, philosophy goes from a subject who thinks to a thought object, and This is a big deal! But the discussion of that issue goes too far from our porpoise in this short biography. He is the hinge that closes the door of the medieval world and opens the modern one! Born in La Haye in Touraine (now this town is called Descartes), Indre-et-Loire, France on 31 March 1596 from a noble family: Joachim, lawyer , and Giovanna, who died when he was thirteen months old. He spent his early years with his grandmother, older brother and sister, Pierre and Jeanne. Little Descartes grew up in a careful environment given his sickly character. At the age of 8, he moved to the city of La Fléche to attend the prestigious Jesuit school until 1614, where he studied grammar, Latin and Greek, in-depth studies of classical literature, physics and mathematics, and will also be impregnated by the philosophy of Aristotle , but already filtered by the school vision. At that time the city and the intellectual world that surrounded it were moved by the discovery of the moons of Jupiter by Galileo Galilee, in 1610. Like his father and some others...... middle of paper...... ce, mathematics, physics, biology and geometry are dismembered from the trunk of philosophy and begin their journey as separate sciences. But, more profoundly, he is the founder of Idealism, the system that begins a new era in philosophy, because in ancient and medieval philosophy we believe in the existence of things, res, by themselves, independent of me. ; but with Descartes we begin to believe in the existence of things only if they are in relation to me, if they exist in my mind, thus giving life to a new way of seeing life, a new way of approaching the world, which will lead us to be materialized later in the French Revolution, where personal beliefs prevail over God-given beliefs. In conclusion, Descartes is one of the greatest thinkers of all time, changing the way we see the world, the way we understand religion, funding new ways of understanding objects, etc.