Physicists, mechanic, mathematician, and metaphysical philosopher Reńe Descartes (1596-1650), lived in a period of great changes.
Descartes wanted to have a reliable bases for the foundation of science. That is why he wanted to engage in metaphysics. His foundation for science was found on God. He lived in a period and a place where doubt, regarding God, authority, and the church was strong. We are taking about the French Enlightenment.
He reaches his thesis for God as the foundation in a strange way. His method was to use doubt. He was not a skeptic but he decided to construct a method of doubt. Doubt everything, even the five senses. That is the method.
Having reached the extreme of doubting, Descartes realizes that in his ‘Discourse on the method’ that “I am thinking, therefore I exists”, even doubting everything’s existence leads him to this reality, that thinking is evidence for existence.
This view and quote is well known, but it is limited to himself, his thinking, his own achieved philosophy. It is a subjective starting point. How he gets out from himself to everyone and everything else is, God.
He developed a mathematical physics. His medieval physics was the common one of the time, in which God was the center of everything. His secure foundation for philosophy, knowledge, and science, is, “I exist therefore God exists”. My own existence is a reminder of my own weakness, and finiteness. Which makes me aware of a sense of something beyond himself, something infinite, and yet something quit like himself.
Descartes realizes that he is not alone and he can see himself forward into a reliable system of knowledge. He understood first the principle that man can not trust his senses, because the bible says that man is in a fallen state. He then goes with the idea that because God in fact created the mind, making it capable of careful reasoning, that he has a way to go about his philosophy, and mathematics. Mathematics become his step by step, rational approach to gaining knowledge. Mathematics if used carefully, following the rules, is his key to truthfully and accurately pursuing knowledge.
His development of physics, in terms of accurate particles; size, shape, motions. Descartes stressing of the finiteness of mans mind and his limits was what kept his science in check.
His unified organic system of knowledge excluded the consciousness. He believed it could not be measured in the way that everything else was measured and observed. This lead to his own version of dualism. Two radically different ideas of reality; extension and conscious thought. So things that can be measured and things that can not be measured.
Descartes ideas about conscience thought are often confused with someone interjecting religious ideas into philosophy. However, Descartes had it seems, reached a point in his philosophy that he felt that thought, and ideas was not simply a mechanical feature of the human mind.
He knew that life and thought was inseparable from the body. He did not see humanity as angelic. He understood that conscious was not simply thought but, pain, hunger, thirst. It is the signature of our humanity. Not simply an spirit in a human body. Mind and body make up a special unity, the material, and the metaphysical nature.
Descartes was very aware that the nature of the relationship between body and mind was not something needing to be philosophically arranged but it was to be experienced. Everyone experiences the relationship with mind and body.
Descartes learned that there were things that could not be measured mechanically. But that does not mean they can not be experienced. He never set out to prove Gods existence. But according to his own philosophy, and experience we believed God was a reality much like the conscience. God is something we know exists, and experience regularly, but can not be measured with mathematics, physics, and science.
Obviously today many attempt and achieve good science without God as long as rules are followed, truth is pursued, and care is exercised. But what is clear from the example of Descartes is that God is not a delusion that hinders the concept of science, philosophy, mathematics, physics, est.