Under such conditions...
Under such conditions, a social and intellectual order is needed that will free the thoughts and acts of human beings from the wearying and stultifying burden of attachment and give shape and direction to their constant exertions in the realm of both thought and action. The eternal miracle that is the Noble Quran sets forth the main principles of such a system by following which human being is able to advance.
Among all the heavenly books, the Quran is the only one to have withstood the ravages of time so that we have in our possession a complete and uncorrupted text clearly reflecting its abundantly creative teachings. The Quran itself proclaims: “We it is Who have sent down this Quran and We it is Who will protect it.” (2) This verse indicates that the most important reason for the sending of new Prophets no longer obtains.
In addition, we should be aware that belief in all the Prophets signifies belief in a continuous historical process, one which began with history itself and the origins of human society has expressed itself in a struggle between truth and falsehood and will continue until the final triumph of the former over the latter. In each age, the Prophets have advanced the awareness and maturity of human beings in accordance with the circumstances and capacities of society.
Differences with respect to certain laws and ordinances do not touch on the fundamental principles and nature of religion because this apparent lack of harmony relates to subsidiary matters, not fundamental concern connected with the very nature of religion. To correct deviations in thought and belief is possible, in fact, only if a variety of programs of action, each congruent with a set of objective realities, are adopted.
If an apparent lack of harmony can be observed in the methods followed by the Prophets in the course of their continuous efforts, this has no connection with their fundamental aim. There is no contradiction among their missions with respect to the principal goal-changing and forming anew the thoughts of human beings who had lost touch with reality and were living in darkness, both culturally and socially.