This is why the Christian God, the Jewish God, Buddha or any African God, for example, are wise, just and powerful1. All of man's characteristics are gathered and joined in a larger than life, larger than man figure, with all of these characteristics projected on a grand, infinite scale. Feuerbach himself states that God is "of man's species-essence, the totality of his powers and attributes raised to the level of infinity"2.
Feuerbach's atheism may, for some part, resemble the classical atheism to which Marx himself adheres. However, we may notice that in Feuerbach's case, God is not a non-existence, he is a creation. We may argue that Feuerbach implies the creation by a small group of people (the clergy, the religious class that exists in every society) of an infinite figure that will reflect the ambitions and needs of the entire mankind. Gods are images of the people itself and, in this sense, will reflect the main characteristics of those people.
So far, we have stated that, according to Feuerbach, God is an image of man. Nevertheless, we are aware that in all monotheistic religions, God is the Supreme Being of the existential Universe, the most powerful element of the Universe. A creation of man has become more powerful than the Creator itself. Substituting the Creator and the Created, Feuerbach states that it was man that created God and not the other way around. This anti-theological (I would not consider it necessarily atheist, looking at atheism in its stricto-sensum definition of denying God's existence altogether) paradox leads to alienation: man is separated from its own creation, which has become more powerful than himself. For Feuerbach, the subject (man) has become the object, hence the state of alienation in which he finds himself.
Marx intervention is not necessarily on the conceptualization of religious alienation, but on the causes of this religious alienation that Feuerbach has defined and justified as a product of man's spiritual creation, God. Marx goes further than this, one step ahead in judging religious alienation. Spiritual religious alienation was a product of mankind creating God, but the actual cause of this was related to material alienation that was only the characteristic of the real world. Material alienation, the existence of social and economic inequality in the real world, led Christians to create the Kingdom of Heaven where everybody is equal and a just God who looks onto Earth and only lets the poor in Heaven.
We have to turn at this point at Marx's "Theses on Feuerbach", essential work refuting Feuerbach's philosophical concepts of alienation and, in my opinion, the fourth point is fundamental in Marx's negation of Feuerbach's concept of alienation. It states, referring to Feuerbach's framework with two worlds, religious and secular, that "the secular basis detaches itself from itself and establishes itself as an independent realm in the clouds can only be explained by the cleavages and self-contradictions within this secular basis"3.
As such, in Marx's opinion, the alienation/duplication between the secular and religious worlds needs to be followed by a subsequent recognation of the allientaion/duplication of the secular world itself. The religious world is a projection of the secular world (this is Feuerbach's idea sustained by Marx), but the the secular world itslef has alienation processus whose causes need to be analyzed.
So, we may at this point refer