As one of the most brilliant epic in English literature history, Paradise Lost deals with the fall of man, which includes Satan and his downfall in both Heaven and Hell. It also gained Milton his world fame. This thesis is aimed at discussing the reason for the fall of man and the importance of knowledge. In the begin part of Paradise Lost, John Milton clarified his purpose of writing this poem. He said, “I may assert the Eternal Providence, and justify the way of God to men.”(Book 1, 25, 26) There are two important ideas: “Eternal Providence” and “the way of God to man”. The main characters of this epic are Satan, Eve and Adam. And the story among them three focus on the forbidden fruit off the tree of Knowledge. To eat or not to eat, it’s a question. Satan derived Eve into eating. Eve hesitated at first, but could not resist the temptation of eating at last. Adam ate the fruit out of his love to Eve. So, we may consider the Providence as the forbidden fruit, which stands for the knowledge of good and ill. As a result, the knowledge becomes the key to explain the reason for the fall of man. According to St. Augustine, there are two levels of knowledge. He designates these two levels as “sense knowledge” and “contemplation knowledge”. The lower level is said to be attainable by human senses, while the higher level is said to be supersensible and thus only attainable by means of God’s illumination or analogical interpretation. The two levels have been represented in Adam’s talk with Raphael. After Raphael’s arrival at Eden, Adam asked him a lot of things, such as the genesis of the world and God’s contribution. However, in their talks we notice that when Adam asks about the earthly things, Raphael will answer easily and happily, but when Adam asks about the heavenly things like the operation of the stars, Raphael will answer hesitatingly and with some reserve. At last, Raphael advised Adam: “And thy fair Eve; Heaven is for thee too high To know what passes there; be lowly wise: Think only what concerns thee, and thy being; Dream not of other worlds, what creatures there Live, in what state, condition, or degree; Contented that thus far hath been revealed Not of Earth only, but of highest Heaven.”(Book 8, 172-178) Raphael emphasized the virtue of modesty in knowledge-seeking and even pointed out the bad consequence of over-curiosity to Adam. At that time we may ask: why did Raphael forbid the knowledge which Adam was curious about? In order to answer it, let us come back to Paradise Lost. When Adam and Eve were first created by God and sent to Eden, God warned them: “But of the tree whose operation brings Knowledge of good and ill, which I have set The pledge of thy obedience and thy faith, Amid the garden by the tree of life, Remember what I warn thee, shun to taste, And shun the bitter consequence: for know,” (Book 8, 322-327) God wanted man to obey his command to show obedience and faith. Though he sent Raphael down as the “Divine Interpreter”( Book 7, 72) to illuminate heavenly things to Adam on the analogy of earthly things, he didn’t really want man to gain the knowledge. Knowledge could broaden the horizon of man’s brain and make man think more about the life and the world. It may become unstable factor in God’s control. So God would not let man gain the “knowledge of good and ill”( Book 8, 323). We can find some clue from Satan’s words: “He knows that in the day Ye eat thereof, your eyes that seem so clear, Yet are but dim, shall perfectly be then Opened and cleared, and ye shall be as Gods, Knowing both good and evil, as they know, That ye shall be as Gods, since I as Man,” (Book 9, 706-710) He told Eve that knowledge of good and ill could make her know how to approach good and shun evil, could thus lead her to a happier life, and could make her Gods’ equal. The truth is that if man gains the knowledge of good and ill, they would have only some ability as God, and at the same time, God would not be superior to man as before. So Adam and Eve were forbidden to eat the fruit on the tree of knowledge. But God forgot one important thing. That was curiosity, which was human’s nature. Though in the former part Adam had been so impressed by Raphael’s warning, Eve committed the very sin of intemperance in knowledge-seeking for succumbing to Satan’s temptation to eat the fruit of the Tree of Knowledge. So, the superficial reason for the fall of man is curiosity, but exactly the true reason is that God’s forbidding forced man to fall. God was afraid of man gaining knowledge. It reminds us of the Emperor Qin. He burned the books and buried the scholars alive in order to consolidate his rule. Knowledge showed its power in this event. The Emperor Qin was afraid that people would learn knowledge from the books and began to revolt against him. He was afraid that the scholars would spread their knowledge to plebeian and the whole country would not obey his rule. God had the same thought as the Emperor Qin. They both wanted to deprive man’s right of seeking knowledge, but they both failed in some way: people of Qin dynasty tried their best to learn from others under the authoritarian rule; Adam and Eve ate the fruit of the tree of Knowledge and gained the knowledge of good and ill, though they were driven out of Eden. Man’s nature of seeking knowledge would not be wiped out completely, and once they obtain the knowledge, they would have great power to change the world. It is just like Francis Bacon’s famous saying goes: knowledge is power. The desire of seeking knowledge prompts man to try new method, view the world in new aspect and do something they would never do before. So Eve ate the forbidden fruit to pursue the knowledge. The knowledge itself can instruct man in every aspect of life and the whole world. It helps man form his own character and makes man a true man. As for Paradise Lost, after eating the forbidden fruit, Adam and Eve knew the difference between good and ill. They became true men who had own thought and no longer listened to God unconditionally. What’s more, the power of knowledge in particular lies in its application. After driven out of Eden, Adam and Eve initiated man’s history by using of their knowledge, which they gained from eating the forbidden fruit. To sum up, the real reason for the fall of man is God’s forbidding man seeking the knowledge of good and will and Bacon’s words that knowledge is power is truth.