In the today's world, the differences among cults, religions, tribes, races and tastes are very much. One day, there is a fighting due to differences between two tribes. The other day, two countries are fighting due to political differences. At times, the white-skinned were enslaving the black-skinned due to difference in race and skin color and the black-skinned hated them. There have been differences among cults and religions. Even, the presidents of countries differ in tastes and understanding each other.
In such circumstances, anew thought or movement which solves differences between two groups will attract many fans.
That new and beautiful thought is unity. This method possesses so beautiful appearance and sometimes its interior is also beautiful. Because the people of both sides have been bored of differences and conflicts and are eager to quite differences, thoughts, beliefs and tastes.
Baha'is believe in the unity of religions. That is, the basis of divine religions is the same. Because the basis of all religions is believing in God, living after death, paying attention to rice and admirable morality and supreme humane accomplishments, the basis of all religions is the same.
Although different religions and cultures possess various points of view, Baha'is believe that these differences in opinions are related to a unique phenomenon. The differences among religions and cultures have been attributed to the context and culture in which the message has been spred out. Baha'is believe that great (and even minor) religions of the world which have been formed by the divine manifestations are from the same source. According to the Baha'i teachings, no religions or creed is superior to the other; but the newer religions are closer to the time and spiritual conditions of current human beings. Baha'is believe that other religions are divine ones. Bahaullah has expressed that questioning about the validity of each prophet means denying all religions (and the Baha'i one) and God.
You can observe that this thought and belief has beautiful and deceptive outward.
In the holy Quran, the Almighty God has announced the religions before Islam as null. No prophet has said you can obey your previous prophet. All resolute prophets announced their previous creeds as null. We can't obey each divine religion that we want; but we must search to obey the one which makes us to achieve God.