Nihilism is a theory which affirms the absurdity of life, the non-existence of morale and truth.
Nihilisms consists in believing in nothing.
Since Ancient Greek philosophy, Plato’s three elements The Good, The True and the Beautiful aim at defining the value of things and action. Since then hilosophy is generally built on this to determine the value of things and morale.
We can say nihilism has roots from Antiquity time, especially from the skeptics. Ancient skeptics claim that nothing can be known with certainty, that we cannot prove any truth or morale. Even Socrates had skeptic tendencies by disproving arguments of the fellows he debated with and by claiming he knew nothing.
While skepticism is about the value of truth and philosophy to determine what is true, beautiful and good, nihilism tackles the root of all these notions that we favor instinctively. It is the destruction of truth and belief. The world does not have an objective order but the one we build.
Nihilism was theorized during the 19th century. Nietzsche (1850-1900) was the first to point out nihilism as the enemy of modern civilizations as it destroys the foundations of morale.
We question ourselves based on the above elements and best understanding of the concept.