Nihilism is a philosophy that rejects generally accepted or fundamental aspects of human existence, such as knowledge, morality, or meaning. It is a philosophy of negation, rejection, or denial of some or all aspects of thought or life. The term "nihilism" comes from the Latin word "nihil," which means "nothing". Nihilism is the belief that all values are baseless and that nothing can be known or communicated. It is often associated with extreme pessimism and a radical skepticism that condemns existence.

Nihilism can be traced back to the 19th century in Russia, where it represented a philosophy of negation of all forms of aestheticism and advocated utilitarianism and scientific rationalism. Classical philosophical systems were rejected entirely, and nihilism represented a crude form of positivism and materialism, a revolt against the established social order.

Friedrich Nietzsche is often associated with nihilism, although he did not consider himself a nihilist. Nietzsche argued that the corrosive effects of nihilism would eventually destroy all moral, religious, and metaphysical convictions and precipitate the greatest crisis in human history.

A true nihilist would believe in nothing, have no loyalties, and no purpose other than, perhaps, an impulse to destroy. While few philosophers would claim to be nihilists, nihilism is most often associated with extreme skepticism and the rejection of all authority exercised by the state, by the church, or by the family.

In summary, nihilism is a philosophy that rejects values, morality, and meaning, and is associated with extreme pessimism and skepticism. It is often associated with the rejection of authority and the belief that all values are baseless.