For God knows that in the day you eat of it your eyes will be opened, and you will be like God, knowing good and evil. Genesis 3:5, NKJV.
When Eve saw “that the tree was good for food, and that it was pleasant to the eyes, and a tree to be desired to make one wise, she took of the fruit thereof, and did eat.” It was grateful to the taste, and, as she ate, she seemed to feel a vivifying power, and imagined herself entering upon a higher state of existence. Having herself transgressed, she became a tempter to her husband, “and he did eat” (Genesis 3:6). “Your eyes shall be opened,” the enemy had said; “ye shall be as gods, knowing good and evil” (Genesis 3:5). Their eyes were indeed opened; but how sad the opening! The knowledge of evil, the curse of sin, was all that the transgressors gained. There was nothing poisonous in the fruit itself, and the sin was not merely in yielding to appetite. It was distrust of God’s goodness, disbelief of His word, and rejection of His authority that made our first parents transgressors, and that brought into the world a knowledge of evil. It was this that opened the door to every species of falsehood and error. Man and woman lost all because they chose to listen to the deceiver rather than to Him who is Truth, who alone has understanding. By the mingling of evil with good, their minds had become confused, their mental and spiritual powers benumbed. No longer could they appreciate the good that God had so freely bestowed. Adam and Eve had chosen the knowledge of evil, and if they ever regained the position they had lost they must regain it under the unfavorable conditions they had brought upon themselves. No longer were they to dwell in Eden, for in its perfection it could not teach them the lessons which it was now essential for them to learn. In unutterable sadness they bade farewell to their beautiful surroundings and went forth to dwell upon the earth, where rested the curse of sin…. Although the earth was blighted with the curse, nature was still to be humanity’s lesson book. It could not now represent goodness only; for evil was everywhere present, marring earth and sea and air with its defiling touch. Where once was written only the character of God, the knowledge of good, was now written also the character of Satan, the knowledge of evil. From nature, which now revealed the knowledge of good and evil, humankind was continually to receive warning as to the results of sin.—Education, 25, 26.BLJ 41.6