To this day, the name of René Descartes (1595–1650) is most associated with his famous quote, “I think, therefore I am.”

The phrase appeared in his native French as “je pense, donc je suis” in his seminal 1637 treatise, Discourse on the Method. Even though this concept may sound like a foregone conclusion, it was revolutionary for the 17th century, as it established the link between thinking and existence.

In more than 370 years that followed, this premise had been accepted as self-evident truth, and today nobody disputes that the capacity to think is a fundamentally human trait. (Descartes, needless to say, did not weigh in on the quality of thoughts, but only on their presence).

Although best known of Descartes’ quotes, the French philosopher, mathematician, and scientist, whose 420th birthday is on March 31, also uttered other words of wisdom that still ring true today.

For instance, he said: “Divide each difficulty into as many parts as is feasible and necessary to resolve it.”

Nowadays, the strategy of breaking a complex issue into workable parts has been widely used for problem resolution and critical thinking.

In fact, many of Descartes’ thoughts laid out in his Discourse on the Method, fit in well into various contexts of the 21st century, proving that truth is, in a sense, timeless:

“It is not enough to have a good mind; the main thing is to use it well.”

“To know what people really think, pay regard to what they do, rather than what they say.”

“When writing about transcendental issues, be transcendentally clear.”

All these truisms prove yet another of Descartes’ contentions: that “One cannot conceive anything so strange and so implausible that it has not already been said by one philosopher or another.”