June 8 1637: "I think, therefore I am"

Context

In 1633 René Descartes considers publishing his "Treaty of the World", in which he defends heliocentrism, the idea that the world revolves around the sun. However, after seeing that Galileo was condemned by the Church for supporting the same idea, Descartes refrains from publishing.

Nevertheless, in 1637, he publishes "Discourse on Method", a literary work intended to probe individuals and analyze the extent to which they will accept or defer from the evolutions induced by science.

Let us analyze the most striking points from this work: 

Good sense is the best thing shared in the world

This is the first sentence in "Discourse on Method". In order to understand it, we must consider "good sense" not in its literal meaning, but rather, as our ability to reason, to judge.
Descartes shows through irony, our inability to question ourselves. He makes us realize the extent to which we complain about ourselves. We don't find ourselves rich enough, good looking enough, lucky enough... but rarely do we complain about our lack of judgement, all satisfied with our ability to reason. He highlights it a couple lines later on as well stating: "Everyone considers themselves so gifted that even those who are the most difficult to satisfy, don't desire more reasoning than they already have."

So then how can encourage more self-reflection and questioning?
Descartes aimed to answer this question in his Rules of Method, inspired by math.

The 4 golden rules to think properly

• The rule of the obvious: to not deem anything that can be doubted as a truth
• The rule of analysis: to resolve an issue, it is necessary to break it up in as many parts as possible and solve each individually: starting from the complicated, and ending with the simple
• The rule of synthesis: the opposite of the previous rule. Once all of the parts have been resolved, put them back together in order to resolve the issue as a whole.
• The rule of counting: ensure that the issue has been resolved in its entirety without having omitted anything

These rules allow us to establish our reasoning, but are we truly real? How can we not doubt our own existence?

"I think therefore I am"

The first thing to take note of, is the use of "I". Nothing out of the ordinary for our individualistic society, but during that era, "I" became part of the cultural renaissance that began after the rediscovery of the ancient texts during the fall of Constantinople in 1453.
Descartes uses "I" and not "Him" meaning the king or God, not "us" referring to the community of believers or family, but rather "I", to emphasize the human being as an individual. The individual thus finds himself at the center of his own thought.

The famous "Cogito"of Descartes (from the Latin verb cogitare: to think): "I think that I doubt, thus I think and if I think, then I am" teaches us that we can doubt everything other than our own existence, because doubting is a thought and thinking is proof of our existence.