The real certainty about the truthfulness of the Quran is evident in the confidence that is prevalent throughout it; and this confidence comes from a different approach - "Exhausting the Alternatives." In essence, the Quran challenges the reader to come up with some other explanation. Here is a book made of paper and ink. Where did it come from? It says it is a divine revelation; if it is not, then what is its source? The interesting fact is that no one has with an explanation that works.
As has already been mentioned, there is much information contained in the Quran whose source cannot be attributed to anyone other than Allah. For example, who told Muhammad about the wall of Thul-Qarnayn - a place thousands of miles to the north? Who told him about embryology? When people assemble facts such as these, if they are not willing to attribute their existence to a divine source, they automatically resort to the assumption that someone brought Muhammad the information and that he used it to fool the people. However, this theory can easily be disproved with one simple question: "If Muhammad was a liar, where did he get his confidence? Why did he tell some people out right to their face what others could never say?" Such confidence depends completely upon being convinced that one has a true divine revelation.
Confidence of prophethood
For example, the Prophet had an uncle by the name of Abu Lahab. This man hated Islam to such an extent that he used to follow the Prophet around in order to discredit him. However, about ten years before Abu Lahab died, a short chapter in the Quran was revealed about him. It distinctly stated that he would go to Hell.
In other words, it affirmed that he would never become a Muslim and would therefore be condemned forever. For ten years all Abu Lahab had to do was to say: "I heard that it has been revealed to Muhammad that I will never change - that I will never become a Muslim and will enter the Hellfire. Well I want to become a Muslim now. How do you like that? What do you think of your divine revelation now?" But he never did that. And yet, that is exactly the kind of behavior one would have expected from him since he always sought to contradict Islam.
Another example of the confidence which Muhammad had in his own Prophethood and consequently in the divine protection of himself and his message is when he left Makkah and hid in a cave with Abu Bakr, may Allah be pleased with him, during their emigration to Madeenah. The two clearly saw people coming to kill them, and Abu Bakr, may Allah be pleased with him, was afraid. Certainly, if Muhammad was a liar, a forger and one who was trying to fool the people into believing that he was a prophet, one would have expected him to say in such a circumstance to his friend: "Hey, Abu Bakr, see if you can find a back way out of this cave." Or "Squat down in that corner over there and keep quiet." Yet, in fact, what he said to Abu Bakr, may Allah be pleased with him, clearly illustrated his confidence. He told him: "What do you think of those two with whom the Third is Allah. "
Now, if one knows that he is fooling the people, where does one get this kind of attitude? In fact, such a frame of mind is not characteristic of a liar or a forger at all. So, as has been previously mentioned, the non-Muslims go around and around in a circle, searching for a way out - some way to explain the findings in the Quran without attributing them to their proper source. On one hand, they tell you on Monday, Wednesday and Friday: "The man was a liar," and on the other hand, on Tuesday, Thursday and Saturday they tell you: "He was crazy." What they refuse to accept is that one cannot have it both ways; yet they need both excuses to explain the information in the Quran .
Did the Devil do it
About seven years ago, I had a minister over to my home. In the particular room which we were sitting there was a copy of the Glorious Quran on the table, face down, and so the minister was not aware of which book it was. In the midst of a discussion, I pointed to the Quran and said: "I have confidence in that book." Looking at the Quran but not knowing which book it was, he replied, "Well, I tell you, if that book is not the Bible, it was written by a man!" In response to his statement, I said: "Let me tell you something about what is in that book." And in just three to four minutes I related to him a few things contained in the Quran. After just those three or four minutes, he completely changed his position and declared, "You are right. A man did not write that book. The Devil wrote it!"
Indeed, possessing such an attitude is very unfortunate - for many reasons. For one thing, it is a very quick and cheap excuse. It is an instant exit out of an uncomfortable situation. As a matter of fact, there is a famous story in the Bible that mentions how one day some of the Jews were witnessed when Jesus, may Allah exalt his mention, raised a man from the dead. The man had been dead for four days, and when Jesus arrived, he simply said: "Get up!" and the man arose and walked away. At such a sight, some of the Jews who were watching said disbelievingly: "This is the Devil. The Devil helped him!" Now this story is rehearsed often in churches all over the world, and people cry big tears over it, saying, "If I had been there, I would not have been as stupid as the Jews!" Yet ironically, these people do exactly what the Jews did when in just three minutes you show them only a small part of the Quran and all they can say is: "The Devil did it. The Devil wrote that book!” Because they are truly backed into a corner and have no other viable answer, they resort to the quickest and cheapest excuse available.
Another Example of people's use of this weak stance can be found in the Makkans' explanation of the source of Muhammed's message. They used to say: "The devils bring Muhammad that Quran!" But just as with every other suggestion made, the Quran gives the answer. One verse in particular states, (what means): "And indeed, those who disbelieve would almost make you slip with their eyes [i.e. looks] when they hear the message, and they say, “Indeed, he is mad. But it is not except a reminder to the worlds." [Quran 68:51-52]
Thus it gives an argument in reply to such a theory. In fact, there are many arguments in the Quran in reply to the suggestion that devils brought Muhammad his message. For example, in the 26th chapter, Allah clearly affirms (what means): “And the devils have not brought it [i.e. the revelation] down. It is not allowable for them, nor would they be able.” [Quran 26: 210-212]
And in another place in the Quran, Allah Says (what means): "So when you recite the Qur’an, [first] seek refuge in Allah from Satan, the expelled [from His mercy].” [Quran 16:98]. Now is this how Satan writes a book? He tells one: "Before you read my book, ask God to save you from me.” This is very, very tricky.
Indeed, a man could write something like this, but would Satan do this? Many people clearly illustrate that they cannot come to one conclusion on this subject. On one hand, they claim that Satan would not do such a thing and that even if he could, God would not allow him to; yet, on the other hand, they also believe that Satan is only that much less than God. In essence they allege that the Devil can probably do whatever God can do. And as a result, when they look at the Quran, even as surprised as they are as to how amazing it is, they still insist, "The Devil did this!" Thanks be to Allah, Muslims do not have that attitude. Although Satan may have some abilities, they are a long way separated from the abilities of Allah. And no Muslim is a Muslim unless he believes that. It is common knowledge even among non-Muslims that the Devil can easily make mistakes, and it would be expected that he would contradict himself if and when he wrote a book. For indeed, Allah Says (what means): “Then do they not reflect upon the Qur’an? If it had been from [any] other than Allah, they would have found within it much contradiction.” [Quran 4:82]