You are right, but it was a corruption of what was made pure that caused the fall.
Students of biblical hermeneutics know that even a literal rendering of a passage allows for figurative language considerations when that possibility is plausible. As an example, consider that Jesus declared we must "eat His flesh" and "drink His blood" in order to follow Him (John 6:53). Is that assertion meant to be taken literally? The answer should be obvious. The Bible sometimes does not mean what it says but it always means what it means. The challenge regarding a passage is whether there is an intended meaning, and the way I see it, is that the account of Genesis 3 is both literal with strong metaphorical language. To focus on the forbidden fruit that was eaten, the Bible is quite clear that it is not an apple. And whatever this forbidden fruit was, it ended up eternally damning mankind, Satan, and the entire world. It is also implied elsewhere in the Bible that the original sin was a defilement, a profane action.
2 Peter 1:4 Whereby are given unto us exceeding great and precious promises: that by these ye might be partakers of the divine nature, having escaped the corruption that is in the world through lust.
Corruption means decay, and decay has to have started upon which was originally pure or clean. We all agree that this world is decayed and corrupt and becoming more so everyday? So the question is, when did it die? When did it start to stink? Biblically, it started in the Garden. The NT tells us over and over again that this is where is started, this is the fall. Now how did the corruption come into this world? Through the original sin. What was the original sin? Lust. And we understand that the serpent "beguiled" Eve, that leaves potential connotations of sexual seduction. That is not to say that sexual intercourse was forbidden. "Nakedness" in a context is an idiom for having sexual intimacy and Adam and Eve were known to be "naked and felt no shame," which I tend to take it as metaphorical language.
Metaphorical expressions:
- Fruit
- Eating of the fruit
- Nakedness (both literal and metaphorical?)
- Without shame (both literal and metaphorical?)
- Serpent
- Tree of life
- Tree of knowledge of good and evil
- Tree (both literal and metaphorical?)