Nihilism is the philosophical doctrine suggesting the negation of one or more putatively meaningful aspects of life. Most commonly, nihilism is presented in the form of existential nihilism, which argues that life is without objective meaning, purpose, or intrinsic value. Moral nihilists assert that morality does not inherently exist, and that any established moral values are abstractly contrived. Nihilism can also take epistemological or metaphysical/ontological forms, meaning respectively that, in some aspect, knowledge is not possible, or that reality does not actually exist.