If you know about philosophy, it should be pretty safe to assume you’ve heard the name, René Descartes. After all, if you ask just about anyone, the very idea of modern philosophy can be traced right back to him. As well as being the “Father of Modern Philosophy,” Descartes was also a mathematician and a scientist. This debunks the idea that only creative people are doomed to lie awake at night, overthinking every little thought and feeling. But considering Descartes is behind the idea of “cogito ergo sum,” which we’ll cover later, at least that means we exist.
René Descartes is a philosopher, mathematician, and scientist that was born in France in 1596. Although he was also a scientist and a mathematician, he's primarily known for his philosophical ponderings. Most notably, Meditations on First Philosophy. In Meditations...', Descartes set about seeking doubt in everything that he knew: His family, friends, the food he ate, and the clothes he wore. Even everything he'd learned in school. As a result of his search, he believed that there could be rational arguments for the existence of anything.
There’s a joke between philosophy students. It starts off with Descartes walking into a bar. He asks for a Bourbon, and the bartender asks him if he’d like it on the rocks. Descartes says, “No, I think not.” Then, he disappears. To explain this joke, we have to talk about, “Cogito, ergo sum” or, in English, “I think, therefore I am.” Chances are you’ve heard this before, whether you’re into philosophy or not. However, the trick to understanding it is, ironically, to not overthink it. Descartes set out on a journey to try and discover some wholly universal truth that not a single person could doubt. The only truth he found was that the act of having doubt requires thought which required him to have those thoughts. Therefore, it was true that he existed. In other words, he was his own ultimate proof.
Descartes' doubt-seeking has a name. It's known as "methodological skepticism," and his realization of "I think, therefore I am" made clear to him that alone was the fundamental principle that anything that can be talked about or thought of can be true. Although this might seem like something of a stretch, that conclusion went on to inspire and divide philosophers and logicians alike. In other words, his reach was and is expansive.
Descartes was a major player in the philosophical movement known as rationalism. Rationalism is a method of understanding people and the world by using reason as the means in which to learn. This was also a big part of the era in which René Descartes was doing his thing. Rationalism took the ancient philosophies of Socrates and Plato and turned them on their heads to provide a more understandable philosophical theory. One that anybody could understand.
Descartes excelled at mathematics in school, although he had doubts about the ways in which it was taught. He also took his love of mathematics through to his adult life. In fact, quite a few of the mathematical theories and systems you and I learned about came from Rene Descartes. Those little numbers that tail the end of bigger numbers to denote that something is 'squared' or 'cubed'? That was Descartes. In addition to that, he also introduced what we now know as standard algebra notations.
Those standard algebraic notations didn't just leave a tremendous legacy in the field of math. They're also crucial to many scientific breakthroughs. As a mathematician, he's credited with founding the basis of analytical geometry. Without analytical geometry - also sometimes referred to as Cartesian geometry - we might not have engineering, spaceflight, or even aviation.
In his Meditations..., Descartes offers us two arguments for the existence of God. However, this isn't to say that he had proof of the presence of a bearded man up in the sky. He simply had a belief. Therefore, according to his own theory, God exists.
Although dualism itself was around long before Descartes was a glimmer in the eyes of Madame and Monsieur Descartes, Cartesian dualism is how dualism affects people. Descartes was the first person to put this theory into action with and for men. For example, Descartes believed that a human being consisted of two different things: Mind and Matter. To him, they were different; as were the mind and the brain. Cartesian dualism is the non-presented third option: The brain and the mind being connected.
The problem with this question is that Descartes influenced a lot of subsequent Western philosophies. That being said, some of the philosophers who proceeded him were influenced by his thoughts and his ideas. Whether they were of the same thought as he was or rejected his thoughts entirely, they left their mark on brilliant minds like those belonging to Pascal and Locke.
If you'd like to know more about Rene Descartes and his theories, the best way to go about it is to read his ideas yourselves. As well as Meditations, some other books of his that are worth a read include Discourse on the Method, The World, and Treatise on Man, and Passions of the Soul'. However, Descartes was so prolific in his works that there's a nearly endless supply of offerings.