On one hand...
On one hand, there exists a large group of people who have researched the Qur'an for hundreds of years and who claim, "One thing we know for sure - that man, Mohammed (pbuh&hf), thought he was a prophet. He was crazy!" They are convinced that Mohammed (pbuh&hf) was fooled somehow.
Then on the other hand, there is a group which alleges, "Because of this evidence, one thing we know for sure is that that man, Mohammed (pbuh&hf) was a liar!" Ironically, these two groups never seem to get together without contradicting. In fact, many references to Islam usually claim both theories. They start out by stating that Mohammed (pbuh&hf) was crazy and then end by saying he was a liar. They never seem to realise that he could not have been both!
For example, if one is deluded and really thinks that he is a prophet, then he does not sit up late at night planning, "How will I fool the people tomorrow so that they think I am a prophet?" He truly believes that he is a prophet, and he trusts that the answer will be given to him by revelation. The Critic's Trail As a matter of fact, a great deal of the Qur'an came in answer to questions. Someone would ask Mohammed (pbuh&hf) a question, and the revelation would come with the answer to it.
Certainly, if one is crazy and believes that an angel put words in his ear, then when someone asks him a question, he thinks that the angel will give him the answer. Because he is crazy, he really thinks that. He does not tell someone to wait a short while and then run to his friends and ask them, "Does anyone know the answer?" This type of behaviour is characteristic of one who does not believe that he is a prophet. What the non-Muslims refuse to accept is that you cannot have it both ways.
One can be deluded, or he can be a liar. He can be either one or neither one, but he certainly cannot be both! The emphasis is on the fact that they are unquestionably mutually exclusive personality traits. The following scenario is a good example of the kind of circle that non-Muslims go around in constantly. If you ask one of them, "What is the origin of the Qur'an?" He tells you that it originated from the mind of a man who was crazy.
Then you ask him, "If it came from his head, then where did he get the information contained in it? Certainly the Qur'an mentions many things with which the Arabs were not familiar." So in order to explain the fact which you bring him, he changes his position and says, "Well, maybe he was not crazy.