In plain words
The names of great souls of this kind — the Buddha, Jesus Christ, Zoroaster, Muhammad and others — have come to be. There is truth in saying that their doctrines, ideals and ideas are counted, under their own names, as their respective religions. How so? Because it arose through Jesus Christ, the divine messenger held to be the ideal and foremost among men, they called it the Christian religion and gave it Christ's name. Since the faith arose through the Buddha, they likewise gave it the name 'Buddhism', his own name. And since the ideals and doctrines of Muhammad, who came as a divine messenger, are followed, they gave that faith the name 'Muhammadan religion'. So there is no fault in calling these the ideal, foremost works of man.
The Divine Intelligence is whole and all-knowing; the human intellect is confined within a certain limit — it may fairly be called 'knowing a little'. Although all the scriptures of religion speak of one and the same truth, because they demonstrate it by different paths, room has come to exist for many religions. And because many religions exist, each carries out its own vindication in its own way, each according to its own distinct doctrines. But to say that Rāma, Christ, Zoroaster, Buddha and Muhammad are all simply one and the same will not hold.
These various names point to one and the same reality — that much they do indicate. In the Christian faith it is held that souls were created; that Allāh created the souls is likewise held in Islam; and Zoroastrianism and Buddhism teach almost the same thing. The Vedic religion, however, teaches something different from this. The jīva is eternal. God's own existence and the soul's own existence are bound up with each other — were the soul itself not to exist, God too would not exist: this it declares emphatically. The followers of other faiths are only now beginning to recognize this truth. Between the birth that has passed and the birth yet to come, the present birth stands bound fast; and for the destiny that follows, this present birth is defined as its very foundation. This very matter the Vedic religion states by way of suggestion.