The prism is a wonderful example to demonstrate how does men understand in general. Light goes through the prism and it divides the light into its components according to wavelengths. As a result, colors like red, orange, yellow, green, blue and violet will be formed from the one light. Human understanding is the same. Some understands only the yellow, some only the red and the other understands only the blue. All of them understand well even so they are in constant dispute. If they would put the parts together, it would release the whole light.
Sure, some comments will come that Islam is the light! Of course, but what can Islam do with this light if followers can understand only the red or yellow part of it? On the other hand, followers of other religions have right also to state that Christianity, Judaism or anything else is the light. Moreover, this right is given by the Quran:
The Messenger believeth in what hath been revealed to him from his Lord, as do the men of faith. Each one (of them) believeth in Allah, His angels, His books, and His apostles. "We make no distinction (they say) between one and another of His apostles." And they say: "We hear, and we obey: (We seek) Thy forgiveness, our Lord, and to Thee is the end of all journeys." (Quran 2:285)
This aya was revealed in the “Hujjat al-Wida’a” the last sermon of Prophet (peace be upon him) and reflect strong call for belief and devotion to follow Allah’s will. As last words they sum up the message of prophecy and give general outlook on Islam. They are very important teachings. The only faith is if we believe in Allah and His Angels, His Scriptures and His Prophets. There is no difference between Prophets! Quran uses plural form! Islam is uniting the nations and religions of monotheism. In the last aya there is a common prayer what we say together with all who believe and ask Allah in order to save us from sins and burdens what were committed and carried by those who were before us.
However, the real light would fill our mind if we would put colors together. Then we would recognize the truth in reality. So far, we can perceive only single colors:
But people have cut off their affair (of unity), between them, into sects: each party rejoices in that which is with itself. (Quran 23:53)
The people who began to trade on the names of the prophets cut off that unity and made sects; and each sect rejoices in its own narrow doctrine, instead of taking the universal teaching of Unity from Allah. But this sectarian confusion is of man's making. It will last for a time, but the rays of Truth and Unity will finally dissipate it.