The serpent sets the tone--seductive but also rousing. In none of its appearances is its image simple. It bears poison within itself, but on the Aesculapian staff, healing. It is the dragon of the abyss, but, at another moment, the lightning high-above. And long after it is meant to have brought sorrow on our first parents, the sight of the serpent-idol held aloft heals the children of Israel from leprosy. Nor did it tell lies, as befitted the most cunning of all the beasts of the field, at least not in the most important point of its promise. For it promised Adam he would be like God; and when Yahweh saw him afterwards he said, "Behold, the man is become like one of us, knowing good and evil" (Gen. 3.22). What sort of sin is that, wanting to be like God and to know good and evil? So far is it from being unambiguous, indeed from being sin at all, that countless pious people from that time on would most likely have taken unwillingness to be like God as the original sin, if this text had allowed it. Is not knowledge of good and evil the very same as becoming a man?--as leaving the garden of beasts, where Adam and Eve still belonged? .... But precisely in this passage, the most outstanding in the whole of the "underground" Bible, the glint of freedom is ill-concealed. And all the less concealable in that the forbidden fruit which opens men's eyes is not deadly nightshade, but the fruit of the Tree of Knowledge, and that tree "was to be desired to make one wise" (Gen. 3.6). Again and again in the underground Bible, the serpent stands for an underground movement which has light in its eyes, instead of hollow submissive slave-guilt.
(Ernst Bloch, Atheism in Christianity, 72-3)