All system of materialism or materialistic monism is certainly atheistic i.e. early Greek atomist, post-Socratic cynics, Epicureanism. Some renaissance philosophers like Campanella, the naturalism of the enlightenment. In France; Voltaire, Holbach, Lamettrie, German positivism, monism of 19th century; Vogt, Buchner, Moleschett, Haeckel; left-wing Hegelianism, bolshevism, existentialism, ethics of N. Hartmann, logical positivism, sensualism.
Focus on the analysis of history; Atheism has always being in question. It goes back to the Ionian philosophers who explained national phenomenon in the content of water, are, free etc. these are material phenomenon was explained in the content of God. The later history of the account of this era we see Democritus and Epicurus who was to teach people to keep away from the idea of God for the sake of attaining happiness external tranquility.
The first accused of atheistic view was Socrates in his disbelief in the official gods of Athens. Plato made it resurface again as he argued against it in the â€˜Lawsâ€™. During this ancient era Democritean Materialism in conjunction with Epicurean materialism and cynicism brought this to life again in trying to justify their materialistic philosophical stand.
The medieval era as a theocentric era never talked of atheism rather theism was the greatest enterprise. As evident in the thought of one of the greatest medieval thinkers in the place of Thomas Aquinas who said that the ultimate beatitude or happiness of every intellectual substance is to know God.
There emerged the death of theocentric philosophy when in 17th century since positive scientists like Galileo; Newton Isaac etc came in to usher in a man centered philosophical thought. It continued to 18th century as some French encyclopaedists conglomerated the British empiricism with Descartesâ€™ mechanistic ideology of the universe, David Hume and Immanuel Kant argued against the traditional proofs for the existence of God. Though indirect atheists they were, they limited human knowledge to the experiential level undercutting natural theology and left the existence of God a matter of pure faith. Atheism did not become emphatic while in the renaissance period until the modern era. Modern science was gaining expedience from theology here on this plain we are to meet philosophers like Feuerbach a Karl Marx and Bertrand Russell who saw God as the record of human imagination and proposed the restoration of man to its original place through the eradication of the idea of God. Nietzsche was later to say that God is dead.
It came to its highest point in the 19th -20th century materialist philosophers like Feuerbach, Karl Marx, Stalin, Lenin, Engels etc who stood against the metaphysical position of spiritualism. In the 20th century this lingered in the minds of Jean Paul Sartre, Albert Camus of the existential atheism who continued the view that man is alone in the universe, free to determine his own values. As Sartre will put it â€œhuman freedom entailâ€™s denial of Godâ€ in existence.
Nietzsche Friedrich came with his radical postulatory atheism of the analogy of God that releases humanity to fulfill itself and find its own essence.
Finally comes the positivism and its later development; logical positivist of Vienna circle who saw the propositions concerning the existence or non-existence of God as nonsensical and meaningless because they are talking of existent outside experience.