Nihilism

Nihilism is the belief that there is no objective ground of truth. There are no absolutes and all moral codes and religious beliefs are man-made.

The word was apparently first coined by the Russian author Ivan Turgenev to describe a character who denied anything that could not be scientifically proved. His character, Barazof, was based on members of a radical set of philosophies then current in Russia according to Forrestt A. Miller's article in the Grolier Encyclopedia of 1995:

As materialists and atheists, the nihilists saw contemporary society as existing apart from the harmony of nature, maintaining itself through hypocrisy and lies. Young Russians, therefore, sought to liberate humanity and transform society by behaving in accordance with their true natures.

An article in Funk & Wagnalls Encyclopedia 1995 (INFOPEDIA) generally agrees with the above but also says that the term had previously been used to describe a form of Christian Heresy in the Middle Ages.