When Did Existentialism Begin?

You ask a very good question! When existentialism is thought to have begun is in the 20th century; however, gained popularity in the two decades post WWII. Existentialism is a philosophy that basically makes us responsible for ourselves and the choices we make. To me, and I am no philosopher, the question of when did existentialism begin is when we were old enough to make choices based off the definition. You can find more information here: