It is not possible to formulate a single, comprehensive definition of atheism that will cover all cases equally and adequately.
Atheism took its root from two Greek words â€œAâ€ and â€œtheosâ€ meaning â€œnotâ€ and â€œGodâ€ respectively. This theory held that God is not. In the narrow sense of it; it is defined as not believing in a God. As a wit once in France referred to someone as an atheist because he believes in only one god. If we follow the meaning of atheism as above we definitely will call Christians and Moslems and other religions that believe in the existence of one God atheists. Atheism strictly speaking means a belief that there is no being or existent called God. This is the antithesis of theism, which holds that there is an existent called God. There are various tendencies towards God, although, while some are negative like atheism and some are positive like theism.
Atheism ad immemorial has been rooted in the vast array of philosophical systems. It is actually a large current in the history of philosophy. It essentially lives on the misconception of the ideas of God from which theism in its actual historical forms inevitably suffers. It is at times merely the rejection of a God who does not really exist and a reaction to the atrophy of genuine religious experience or to the theodicy of evil.
In fact atheism arguments presented by the atheists in general is directed against the Christian concept of God and in the long run excludes other possible gods. In the Western World it is very conspicuous that atheism is the doctrine of the non â€“ existence of the Christian God people like Nietzsche, and atheists who only fought the God that western civilization had incarnated and in many areas truncated by imperialism, materialism, individualism, capitalism and like Karl Mark describe religion as the opium of the people. He meant no other religion specifically than Christianity. Atheism proposes positive disbelief rather than mere suspending of belief. There are various gods as object of belief so one may be an atheist to one God and theist to the other god as in the case of a Christian, Moslem, and Judaism etc.
Summarily it is the positive assertion that God does not exist and even if he ever existed he is dead more or less He does not exist because death marks non-existence. I agree with them that God is dead in the heart of men which is evident in their actions and words that does not portray a god based choices
According to Friedrich Nietzsche it is the awe-inspiring catastrophe of two thousand year training in truth, which finally forbids itself the lie of the belief in God. Atheism according to him is love of truth that got out of hand and discovers its own secularization of the real truth: atheism. When you talk of truth what can be said of god who is truth in its being and totality as philosopher like St. Augustine, St. Thomas Aquinas and other large current of the medieval era who saw God as truth and love in essence.
In contemporary, as Sartre puts it, human freedom entails the denial of god, for the existence of god is a threat to manâ€™s freedom to make his own values via real ethical choice. But where is ethical choice outside God because the voice within which compels you to choose a good and right action is a reflection of the indwelling of a supreme being who is good in essence. For Sartre God is an obnoxious nihilism of primitive mentality.