As we know, God has revealed Himself to humanity most fully through the Jewish people and then through the Christian church. Nevertheless, God has left “seeds of the Word” (as St. Justin the Philosopher puts it) in pagan religions and philosophies.
In this way, Jesus Christ is the fulfillment of all human striving for truth, beauty and goodness.
It is easy to see how Jesus Christ is the fulfillment of Judaism. From the time of Adam and Eve God had promised that He would send a redeemer, a messiah to the Jewish people (although it must be added, God also promised that this messiah, though Jewish, would be a redeemer for all people). Through the centuries God defended the Jewish people and sent them many prophets who predicted the coming of the Messiah.
The record of this is the Old Testament. When we compare the Old Testament prophecies with the New Testament, we see that the promises made by God in the Old Testament are fulfilled by Jesus Christ.
It is easy to see how Jesus Christ is the fulfillment of Old Testament prophecy because the prophets and Jesus have the same religious, cultural and linguistic background. It may be more difficult to see how Jesus fulfills pagan religions. But in fact this can be shown. Pagan religions were often polytheistic (believing in many gods). But among the pagans there were also people who instinctively knew there ultimately must be one true God who stands above and beyond the many other gods. We can see that the God of Israel, the God revealed by Jesus Christ to be the dear father of all people is the fulfillment of this human yearning for the one true God. St. Paul shows us this approach in the Acts of the Apostles, which is the history of the early days of the church, when he preaches to the pagans in Athens. In Athens he had seen an altar dedicated “to the unknown God”. This altar expressed the longing of the pagans for the one true God. St. Paul tells them that the God they sought was the God that he preached, the God of Israel who revealed Himself to the world in the person of Jesus Christ. This story can be found in Acts, Chapter 17:16-34. St. Paul says “What therefore you worship as unknown, this I proclaim to you.” (Acts 17:23)
In addition to the search for the one true God, there are other aspects of pagan religions which Jesus Christ fulfills. For example, in the Hindu religion the concept of the avatar. An avatar is God taking on the human form to save human beings. The most popular avatar is Krishna. Love for Krishna has produced wonderful religious hymns and other devotional literature. This seems similar to Jesus Christ who also descended from heaven to save humanity. But there are differences. Krishna only appears human; his humanity is like a mask or costume. But Jesus Christ became a genuine human being, capable of thirst, hunger, tiredness and so on. Jesus Christ never loses his humanity, even after he ascends to heaven.
Beyond this, Christ is historical in a sense that Krishna is not. Jesus Christ came into the world in a particular historical setting and even non-Christians scholars recognize that Jesus is a historical figure, although of course only Christians see this historical figure as God incarnate.
The study of how Jesus Christ fulfills all genuine human religious striving is incredibly rich. We can see how Jesus Christ fulfills many aspects of many different religions.
Of course, this is a Christian point of view. Jews do not think that Jesus is the fulfillment of Judaism and pagan believers also do not believe that Jesus fulfills their religion and will be offended if we tell them this. However, by seeing Jesus Christ as the fulfillment of all that is good and true in humanity, we can open to truth wherever we fine it and see Jesus Christ as the fulfillment of this truth.