At that time, the religious tradition in France was still relatively strong. He knew that his thoughts were very different from those of the church and would be regarded as heresy in France. In order to write down his research results, he decided to settle in the Netherlands in the autumn of 1628. In Holland, he lives in a remote area of an unknown village or city, not far from universities and libraries. In addition to studying mathematics and philosophy, he also engaged in optics, chemistry, physiology, meteorology and astronomy, and maintained close academic ties with leading European scholars. Almost all Descartes' works were written in Holland. 1628 wrote Principles of Guiding Philosophy, and 1629~ 1634 completed the main part of On the Universe based on Copernicus. He also compiled three papers-landmark works in the history of mathematics: geometry, elasticity and meteorology.
Descartes summed up the research methods of outstanding natural scientists in methodology, summarized and demonstrated them in philosophy, and put forward a deductive method with mathematical methods as the core.
At the end of 1649, Descartes began to be invited to teach philosophy to Queen Christina. Because he often braved the biting cold wind to give lessons to the Queen, in February of the following year 1 he caught a cold and immediately turned to pneumonia. Descartes died in February of 1 1 at the age of 54.
His epitaph reads: "Descartes, the first person who fought for and guaranteed rational rights for mankind since the European Renaissance."