What is Marx saying here?

[Harlow_Jem]

"Once the essence of man and of nature, man as a natural being and nature as a human reality, has become evident in practical life...the quest for an alien being above man and nature becomes impossible...Atheism is the negation of God and seeks to assert by this negation the existence of man."

I get his general philosophy but can't quite grasp exactly what he's saying here and this quote is taken out of context so I can't go back and figure it out since I don't know when or where he said it.

And how does it relate to his philosophy on the whole?

 

[Jack Flak]

He's saying "Religion is incompatible with the modern world," I think.

 

[Owl]

He's saying belief in God is incompatible with belief in the true essence of man. That is, if one wants to know what it truly means to be human, one must first deny the existence of God.

 

[Haight]

"Once the essence of man and of nature, man as a natural being and nature as a human reality, has become evident in practical life...the quest for an alien being above man and nature becomes impossible...Atheism is the negation of God and seeks to assert by this negation the existence of man."

- (A reference to "Man in the state of nature.")
- Man is of nature.
- The reality of nature as a perception of man is that which is evidenced by man's senses.
- As such, evidence is the essence of human reality. Hence, such things that have an absence of evidence become impossible to find.
- (The last sentence is self-evident. *smiles)