Simone de Beauvoir
French existentialist writer and feminist Simone de BeauvoirGetty

By celebrating World Philosophy Day each year, on the third Thursday of November, UNESCO underlines the value of philosophy for the development of human thought, all cultures and for each individual.

"Faced with the complexity of today's world, philosophical reflection is above all a call to humility, to take a step back and engage in reasoned dialogue, to build together the solutions to challenges that are beyond our control," said Irina Bokova, UNESCO director-general.

"This is the best way to educate enlightened citizens, equipped to fight stupidity and prejudice. The greater the difficulties encountered, the greater the need for philosophy to make sense of questions of peace and sustainable development."

World Philosophy Day was established in 2005, to highlight the importance of the discipline to young people, underlining that "philosophy is a discipline that encourages critical and independent thought and is capable of working towards a better understanding of the world and promoting tolerance and peace".

In celebration of the day, IBTimes UK looks at some of the most famous philosophical quotes.

"The unexamined life is not worth living" – Socrates

"One is not born, but rather becomes, a woman" - Simone de Beauvoir

"The life of man is solitary, poor, nasty, brutish, and short" – Thomas Hobbes

"If a tree falls in the forest and no one is there to hear it, does it make a sound?" – Bishop George Berkeley

"One cannot step twice in the same river" – Heraclitus

"Man is condemned to be free" – Jean-Paul Sartre

"The brave man is he who overcomes not only his enemies but his pleasures" – Democritus

"The aim of art is to represent not the outward appearance of things, but their inward significance" - Aristotle

"Is man merely a mistake of God's? Or God merely a mistake of man's?" – Friedrich Nietzsche

"History repeats itself, first as tragedy, second as farce" - Karl Marx

"This has always been a man's world, and none of the reasons that have been offered in explanation have seemed adequate" - Simone de Beauvoir

"The sad truth is that most evil is done by people who never make up their minds to be good or evil" - Hannah Arendt