The Tree of The Knowledge of Good and Evil
You are free to eat from any tree in the garden, but you must not eat from the tree of the knowledge of good and evil. For if you eat from it, you will certainly die.
In my honest opinion, The Tree of the Knowledge of Good and Evil wasn't actually a tree that could be eaten from. It was just a reference, a guide, or you could say it was a warning. A warning that if you were to adhere to the lessons of good and evil, receive it's teaching, believing wholeheartedly that there is the such-ness of good and evil, then the various aspects that make up the wholeness of this one life that you are, would appear to be become divided and separated into one part good, and one part evil.
God warned that if Adam ate from the Tree of The Knowledge of Good and Evil, then he would come to know the knowledge of good and evil - the message was just that simple. Adam would come to label the world around him as being either good or evil. And Adam would remain trapped within the vicissitudes of these two polarities - good and evil. He would live a life of delusional suffering, torn between what appears to be good and what appears to be evil. A life of absolute confusion and disarray. Never again waking up to realize that nothing is actually good or evil. And that all is equally an aspect of this one whole of life.
In the Bible, one of the very first things that God spoke to man about, was enlightenment.