The relative value of any given system of religious thought must depend on the amount of truth which it embodies as well as on the ethical standard which its adherents are bidden to follow. Another important test is the degree of originality that is to be assigned to it, for it can manifestly only claim credit for that which is new in it, not for that which it borrowed from other systems.

With regard to the first-named criterion, there is a growing opinion among students of religious history that Muhammed may in a real sense be regarded as a prophet of certain truths, though by no means of truth in the absolute meaning of the term. The shortcomings of the moral teaching contained in the Koran are striking enough if judged from the highest ethical standpoint with which we are acquainted; but a much more favourable view is arrived at if a comparison is made between the ethics of the Koran and the moral tenets of Arabian and other forms of heathenism which it supplanted.