Critique and denial of metaphysical beliefs in God or divine
beings. Unlike agnosticism, which leaves open the question of
whether there is a God, atheism is a positive denial. It is
rooted in an array of philosophical systems. Ancient Greek
philosophers such as Democritus and Epicurus argued for it in
the context of materialism. In the 18th century David Hume and
Immanuel Kant, though not atheists, argued against traditional
proofs for God's existence, making belief a matter of faith
alone. Atheists such as Ludwig Feuerbach held that God was a
projection of human ideals and that recognizing this fiction
made self-realization possible. Marxism exemplified modern
materialism. Beginning with Friedrich Nietzsche, existentialist
atheism proclaimed the death of God and the human freedom to
determine value and meaning. Logical positivism holds that
propositions concerning the existence or nonexistence of God are
nonsensical or meaningless.