Because of its similar design, it is thought the Cosmic Cross, that appeared in mosaics prior to the year 427 A.D was the insiration for the Jerusalem Cross symolizing the four principal parts of the word. Early Christians believed then that larger and center cross represented the supreme majesty of christ, who is at the center of our universe. The cross has, over the years, been offered up for many different meanings. One example of this is the that the five crosses symbolize the five woundes of Jesus, There is aslo the preception the the four crosses proclaim the fourcorners of the earth with first and largest one beginning in Jerusalem and symbolzing christ. 
Another idea is that the central cross reminds people of the crucified christ, the saivor of our world, and that the four smaller ones represent the four Gospels (Mathew, Mark, Luke, and John). Or they may represent how these gospels were spread to the four corners of the earth. Lastly, there is another symbolizing the four directions of the world and the concept that Jerusalem is the spiritual center of the world. 
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