The foundation of irreligious criticism is: Man makes religion, religion does not make man. Religion is, indeed, the self-consciousness and self-esteem of man who has either not yet won through to himself, or has already lost himself again. But man is no abstract being squatting outside the world. Man is the world of man – state, society. This state and this society produce religion, which is an inverted consciousness of the world, because they are an inverted world...Religious suffering is, at one and the same time, the expression of real suffering and a protest against real suffering. Religion is the sigh of the oppressed creature, the heart of a heartless world, and the soul of soulless conditions. It is the opium of the people.The abolition of religion as the illusory happiness of the people is the demand for their real happiness. To call on them to give up their illusions about their condition is to call on them to give up a condition that requires illusions. The criticism of religion is, therefore, in embryo, the criticism of that vale of tears of which religion is the halo.Criticism has plucked the imaginary flowers on the chain not in order that man shall continue to bear that chain without fantasy or consolation, but so that he shall throw off the chain and pluck the living flower. The criticism of religion disillusions man, so that he will think, act, and fashion his reality like a man who has discarded his illusions and regained his senses, so that he will move around himself as his own true Sun. Religion is only the illusory Sun which revolves around man as long as he does not revolve around himself.

~ Karl Marx

The mystery of this courage of Bauer’s is Hegel’s Phenomenology. As Hegel here puts self-consciousness in the place of man, the most varied human reality appears only as a definite form, as a determination of self-consciousness. But a mere determination of self-consciousness is a “pure category,” a mere “thought” which I can consequently also abolish in “pure” thought and overcome through pure thought. In Hegel’s Phenomenology the material, perceptible, objective bases of the various estranged forms of human self-consciousness are left as they are. Thus the whole destructive work results in the most conservative philosophy because it thinks it has overcome the objective world, the sensuously real world, by merely transforming it into a “thing of thought” a mere determination of self-consciousness and can therefore dissolve its opponent, which has become ethereal, in the “ether of pure thought.” Phenomenology is therefore quite logical when in the end it replaces human reality by “Absolute Knowledge”—Knowledge, because this is the only mode of existence of self-consciousness, because self-consciousness is considered as the only mode of existence of man; absolute knowledge for the very reason that self-consciousness knows itself alone and is no more disturbed by any objective world. Hegel makes man the man of self-consciousness instead of making self-consciousness the self-consciousness of man, of real man, man living in a real objective world and determined by that world. He stands the world on its head and can therefore dissolve in the head all the limitations which naturally remain in existence for evil sensuousness, for real man. Besides, everything which betrays the limitations of general self-consciousness—all sensuousness, reality, individuality of men and of their world—necessarily rates for him as a limit. The whole of Phenomenology is intended to prove that self-consciousness is the only reality and all reality.

~ Karl Marx