“Knowledge of good and evil” in the book of Genesis may not mean realizing the truth that good and evil already exist. Knowledge of good and evil is not a “fall from innocence” in the sense that one had not heard of or even imagined evil but then comes to know of it. The knowledge of good and evil comes about in the context of a non-dualistic universe where there is only good, and it needs no evil to set it off, to be its foil. But to know good and evil is to fracture good into both, to create evil, unnecessarily.
The “knowledge” of good and evil here is not only an abstract knowledge, but more like “cleaving unto,” a knowledge in the erotic sense. One emerges in a fallen world where good seems to need evil (even in the imagination) to exist as good. This may well be the greatest evil of the situation. (See also Ursula Le Guin’s “The Ones Who Walk Away from Omelas” as a marvellous exploration of this idea of “necessary evil.”) One is leaving behind the knowledge (in both senses of that word) of an entirely good world, to a world where this pure good cannot be imagined, cannot be made workable, even as a theory. To the fallen world, the world where good and evil are known, a world of pure good seems an absurdity.
It is in this context then, that in order to save us from this situation, to restore us to a world without evil, Christianity offers the solution of belief in Christ. At this point the words of Francois Jullien become illuminating:
“Because it involves ipseity—selfness in itself—believe takes on a whole other meaning. ‘Believe in’ (pisteúein eis, πιστευειν είζ), John often writes. And, in fact, everything rides on the shift from ‘believing that’ [croire à] to ‘believing in’ [croire en]. What we believe when we believe that is from the start limited, constrained, objectivized (even when the belief is that God exists). But believing in—i.e., in a self, in an ipseity—is not undefined but infinite. When I say ‘I believe in you’ I have no limit in view. Moreover, believing that can be detailed and itemized: I can believe that X is and not that Y is, and thus make a selection. But belief in is by necessity whole; it calls for an absolute. When I say that I believe in you I no longer wonder “what” in you I believe in. To put things differently, believing that entails a necessary measure of credulity, even if I have good reason to believe, because I might just as easily not believe what I believe. I recognize its hypothetical character (e.g., belief that Santa Claus exists). Whereas belief in is not credulous but trusting. By the phrase ‘believe in yourself’—one that a parent might say to a child, or vice versa, or that one lover might tell another—I mean that I am counting on you, that I am expecting something of you, that I am placing my hopes in you, in you as yourself, in your ipseity, or that I am expecting everything of you. Thus belief in entails a self, an ipseity, on both sides. When I believe in someone I involve the entirety of myself. What I believe in in the person in whom I believe is what he himself reveals of himself, but also what he conceals within. Belief that might be open to convincing, but its truth will still rest on insufficient grounds; I would prefer knowledge that was certain. But the truth of belief in, precisely because it entails an as-in-oneself, will not be measured by a truth subject to proof; it is its own guarantee and can claim no other. You must believe in me, says Christ, and not believe what they say of me. But hasn’t the Church, with its dogma, been compelled to shift from belief in (ipseity) to belief that (identity)—and made the latter into the ‘faith’ that tempers its armor?”
(Francois Jullien, Resources of Christianity English edition, 2021, Polity Press, pp. 82-84)