What Was the Forbidden Fruit?

       There have been many interpretations of the Fall, and the books on the subject would fill a small library. The majority of the early Christian fathers held the Mosaic account to be historical, and interpreted it literally, believing that an actual fruit of some kind, not definitely known, was eaten by our first parents. A few early writers, Philo among them, regarded the story of the Fall as symbolical and mystical, shadowing forth allegorical truths, and that the serpent was the symbol of pleasure, and the offense was forbidden sensuous indulgence. Whatever the "fruit" may have been, its use was plainly the violation of a divine prohibition, the indulgence of an unlawful appetite, the sinful aspiration after forbidden knowledge. Professor Banks, several years ago, while traveling in the region of the Tigris and Euphrates, found in a little known district a place which the natives declared to be the traditional site of Eden and a tree (name and species unknown) which they believed to be the successor of the original tree of knowledge, and it was venerated greatly. It bore no fruit. 

• What was the forbidden fruit that Adam and Eve were told not to eat? Was it an apple, like I've heard people say? I like apples, but does this mean I ought to avoid them?
• The Tree of Life and the Tree of the Knowledge of Good and Evil