God instructs us in his Word to test the prophets and we find in scripture not only clear criteria for this testing but also reports of many true and many false prophets so that we have examples that help us in this evaluation.
To test whether a prophet is from God or a false prophet we have to look at both, his message and his life. Muslim theology itself acknowledges the importance of the lives of the prophets as an essential part of the criteria to evaluate the legitimacy of a prophetic claim so much so that it has created the doctrine of the sinlessness of the prophets which goes much further than the Biblical criteria.
There have been many people claiming prophethood both before and after Muhammad. Muslims easily reject the prophetic claims of Joseph Smith (founder of the Mormons, no relation to Islam), Baha'ullah (Bahais, acknowledging Muhammad as true, but moving on to further revelation) and the Mirza Ghulam Ahmad (Ahmadiyya, understanding himself to be a reformer of Islam, not with new revelation) based on the "easy" criterion that Muhammad said there will be no prophet after him.
Even though Muslims will certainly not be pleased by the material linked from this page, nor might they agree with us on the criteria for this test, we hopefully can agree that claims to prophethoood need to be tested whether the claimant's message truly comes from God or not, and this includes theclaims of Muhammad about himself and his message. We will provide references to Muslim sites and their view about Muhammad and why he is a true prophet. But in those presentations a number of issues are regularly left out. A true evaluation has to deal with all the facts and cannot be satisfied with a selective presentation.
These articles are not written to aggravate Muslims, even though this is probably the section on the "Answering Islam" site which will produce the strongest (emotional) reactions. Our sincere hope is that the material will help both Muslims and Christians come to a more realistic evaluation and view about Muhammad based on a fuller presentation of evidences from the sources. In that respect, I hope that even Muslims will find the material helpful for themselves to not be ignorant regarding parts of their history.
Read more: http://answering-islam.org/Muhammad/