What is the Tree of the Knowledge of Good and Evil, first introduced in Gen 2:9, and why is eating of it forbidden, even deadly (2:17)?

This is a profound and important question. One might go on.—Why is it not called the Tree of Death, since it is so closely contrasted with the Tree of Life? And what is wrong with knowledge, even knowledge of good and evil? Are we forbidden to study ethics? Does Proverbs not enjoin us to seek wisdom? Does Jesus not instruct us to be “wise as serpents, and harmless as doves” (Matt. 10:16)?—The way to deal with all such questions is to produce the right theory regarding the symbolic meaning of the tree. It was the only forbidden thing on earth at the time. By making it available, God was, it seems, testing man—here, to be carefully distinguished from tempting man—who failed the test. Thereby God acknowledged man’s free will. To come to the point, then, eating from the tree represented not merely breaking God’s first commandment; it represented our freely substituting our own judgment, and our pretensions to be able to judge what is good and evil for ourselves. So the tree brought death, true, but it brought it by respecting man’s free choice. Since Adam and Eve were initially sinless and innocent, like children, eating from the tree was very like the first act of childhood rebellion against authority. In response, God repaid the rebellion by removing his protection and caretaking. Fruit of this tree resulted in a kind of knowledge of good and evil in the intimate sense of directly experience of deciding what is good and evil, as well as being made to suffer the consequences of rebelliously taking him out from under God’s tutelage. Of course, knowledge and wisdom are good, studying ethics is fine, and we ought to seek wisdom in order the better to do God’s will. What was punished was not seeking after that sort of wisdom, but instead open rebellion against a loving God that, as a side-effect, led to direct experience, and so knowledge, of evil. Indeed, as we will see, Adam and Eve should not have listened to the serpent, and if they were as wise as him, they would not have been taken in. But more about this later.