This paper deals with atheism, Sartre's notion of absolute freedom and Jean-Paul Sartre's claim of the irreconcilability of human freedom with God’s existence. For Sartre, man to be truly human must continuously create his own essence and continuously assert himself. Man can achieve this because he is absolutely free; the affirmation of God would undermine the exigencies of man's freedom and creativity. The question on the impossibility of the coexistence between the affirmation of God's existence and the recognition of human freedom raises certain points against Sartre's notion of God and human freedom. The paper urges the believer to fully understand his beliefs and be also critical of his faith.