Rene Descartes (1596 – 1650) French philosopher and mathematician. Descartes is considered the founder of modern philosophy for successfully challenging many of the accepted wisdom of the medieval scholastic traditions of Aristotelian philosophy. Descartes promoted the importance of using human reason to deduct the truth. This principle of reason was an important aspect of the Enlightenment and the development of modern thought. His work in mathematics was important for the later work of Isaac Newton.

Early Life Rene Descartes

Rene Descartes was born in La Haye en Touraine, France on 31 March 1596. His family were Roman Catholics, though they lived in a Protestant Huguenots area of Poitou. His mother died when he was one year old, and he was brought up by his grandmother and great uncle.

The young Descartes studied at a Jesuit College in La Flèche, where he received a modern education, including maths, physics and the recent works of Galileo. After college, he studied at the University of Poitiers to gain a degree in law.

In 1616, he travelled to Paris in order to practise as a lawyer – according to the wishes of his father. But, Descartes was restless in practising law, he travelled frequently seeking to gain a variety of experiences. In 1618, he joined the Dutch States Army in Breda, where he concentrated on the study of military engineering, which included more study of mathematics.

Visions of a new philosophy

In November 1619, while Descartes was stationed in Neuburg an der Donau, he stated that he received heavenly visions, while he was shut in his room. He felt a divine spirit had infused his mind with the vision of a new philosophy and also the idea of combining mathematics and philosophy.

Descartes had always sought to be independently minded – never relying on books he read; this vision increased his independence of thought and is a characteristic aspect of his philosophy and mathematical work.

In 1620, Descartes left the army and visited several countries before returning to France. He was now motivated to write his own philosophical treatises. His first work was Regulae ad directionem ingenii (1928) Rules for the Direction of the Mind. It set out some of Descartes principles for philosophy and the sciences. In particular, it expressed the importance of relying on reason and the use of mental faculties to methodically work out the truth.

Rule III states:

“As regards any subject we propose to investigate, we must inquire not what other people have thought, or what we ourselves conjecture, but what we can clearly and manifestly perceive by intuition or deduce with certainty.”

– Rene Descartes

Descartes frequently moved in his early years, but he came to settle in the Netherlands, and it was here that he did most of his writings. As well as philosophy, Descartes continued his mathematical studies. He enrolled in Leiden University and studied mathematics and astronomy.

Discourse on the Method

In 1637, Descartes published some of his most important works, including Discours de la méthode. This stated, with Descartes’ characteristic clarity, the importance of methodically never accepting anything as true – which had not been properly examined.

Although Descartes remained a committed Catholic throughout his life, his writings were still controversial for the time period. In 1633, Galileo’s works were put on the prohibited list, and his own Cartesian philosophy was condemned at the University of Utrecht. In 1663, shortly after his death, his works were placed on the Index of Prohibited Works by the Pope.

Ironically, Descartes claimed his meditations were aimed to defend the Catholic faith – through the use of reason and not just relying on faith. However in retrospective, many believe Descartes’ willingness to start with doubt, marked an important shift in philosophy and religious faith. No longer was Descartes stating that the authority of the church and scripture should be assumed – Descartes shifted the proof of truth onto human reason; this was a very influential aspect of the Enlightenment and marked an erosion of authority by the Church.