The tree of the knowledge of good and evil (עֵץ הַדַּעַת טוֹב וָרָע; [Etz ha-da'at tov va-ra]) is one of two specific trees in the story of the Garden of Eden in Genesis 2-3, along with the tree of life.
A cylinder seal, known as the temptation seal, from post-Akkadian periods in Mesopotamia (c. 23rd-22nd century BCE), has been linked to the Adam and Eve story. Assyriologist George Smith (1840-1876) describes the seal as having two facing figures (male and female) seated on each side of a tree, holding out their hands to the fruit, while between their backs is a serpent, giving evidence that the fall of man account was known in early times of Babylonia. The British Museum disputes this interpretation and holds that it is a common image from the period depicting a male deity being worshipped by a woman, with no reason to connect the scene with the Book of Genesis.
The phrase in Hebrew: טוֹב וָרָע, tov V'ra translatable as good and evil, may be an example of the type of figure of speech known as merism. This literary device pairs opposite terms together, in order to create a general meaning; so that the phrase "good and evil" would simply imply "everything". It is equivalent to the Egyptian expression evil-good which is indeed normally employed to mean "everything". In Greek literature, the concept is also used by Telemachus, "I know all things, the good and the evil" (Od.20:309-10). However, given the context of disobedience to God, other interpretations of the implications of this phrase also demand consideration.
In the phrase, tree of the knowledge of good and evil, the tree imparts knowledge of tov wa-ra, "good and bad". The traditional translation is "good and evil", but tov wa-ra is a fixed expression denoting "everything". To Harry Orlinsky, this phrase does not necessarily denote a moral concept. However, Robert Alter believes that there could be a moral connotation after all: When God forbids the man to eat from that particular tree, He says that if he does so, he is "doomed to die". The Hebrew behind this is in the form used in the Hebrew Bible for issuing death sentences.
In Jewish tradition, the Tree of Knowledge and the eating of its fruit represents the beginning of the mixture of good and evil together. Before that time, the two were separate, and evil had only a nebulous existence in potential. While free choice did exist before eating the fruit, evil existed as an entity separate from the human psyche, and it was not in human nature to desire it. Eating and internalizing the forbidden fruit changed this and thus was born the yeitzer hara, the Evil Inclination. In Rashi's notes on Genesis 3:3, the first sin came about because Eve added an additional clause to the Divine command: Neither shall you touch it. By saying this, Eve added to YHWH's command and thereby came to detract from it, as it is written: Do not add to His Words (Proverbs 30:6).
In Kabbalah, the sin of the Tree of Knowledge (called Cheit Eitz HaDa'at) brought about the great task of beirurim, sifting through the mixture of good and evil in the world to extract and liberate the sparks of holiness trapped therein. Since evil has no independent existence, it depends on holiness to draw down the Divine life-force, on whose "leftovers" it then feeds and derives existence. Once evil is separated from holiness through beirurim, its source of life is cut off, causing the evil to disappear. This is accomplished through observance of the 613 commandments in the Torah, which deal primarily with physical objects wherein good and evil are mixed together. Thus, the task of beirurim rectifies the sin of the Tree and draws the Shechinah back down to earth, where the sin of the Tree had caused Her to depart.
In Christian theology, consuming the fruit of the tree of knowledge of good and evil was the original sin committed by Adam and Eve that subsequently became known as the Fall of man in Genesis 2-3.
In Catholicism, Augustine of Hippo taught that the tree should be understood both symbolically and as a real tree - similarly to Jerusalem being both a real city and a figure of Heavenly Jerusalem. Augustine underlined that the fruits of that tree were not evil by themselves, because everything that God created was good (Gen 1:12). It was disobedience of Adam and Eve, who had been told by God not to eat of the tree (Gen 2:17), that was obnoxious and caused disorder in the creation, thus humanity inherited sin and guilt from Adam and Eve's sin.
In Western Christian art, the fruit of the tree is commonly depicted as the apple, which originated in central Asia. This depiction may have originated as a Latin pun: by eating the mālum (apple), Eve contracted malum (evil). It is also possible that this depiction originated simply because of the religious painters' artistic licence.
The Quran never refers to the tree as the "Tree of the knowledge of good and evil" but rather typically refers to it as "the tree" or (in the words of iblis) as the “the tree of immortality”. Muslims believe that when God created Adam and Eve, He told them that they could enjoy everything in the Garden but this tree, and so, Satan appeared to them and told them that the only reason God forbade them to eat from that tree is that they would become Angels or become immortals.
When they ate from this tree their nakedness appeared to them and they began to sew together, for their covering, leaves from the Garden. The Quran mentions the sin as being a 'slip', and after this 'slip' they were sent to the destination they were intended to be on - Earth. Consequently, they repented to God and asked for his forgiveness and were forgiven. It was decided that those who obey God and follow his path shall be rewarded with everlasting life in Jannah, and those who disobey God and stray away from his path shall be punished in Jahannam.
God in Quran (Al-A'raf 27) states: "[O] Children of Adam! Let not Satan tempt you as he brought your parents out of the Garden, stripping them of their garments to show them their shameful parts. Surely he [Satan] sees you, he and his tribe, from where you see them not. We have made the Satans the friends of those who do not believe."
The Tamil poem "Tala Vilasam" recounts a legend of the tree that parallels the Biblical account. In it, the Creator Brahma finally allows the people access to the tree- which, in this case, is the palmyra palmtree Borassus flabellifer.
American ethnomycologist, ethnobotanist, and philosopher Terence McKenna proposed that the Forbidden Fruit was entheogenic, identifying it as the Psilocybe cubensis mushroom, consistent with his "Stoned Ape" model of human evolution.