From the beginning, this one Church has been marked by an extraordinary diversity which comes from both the variety of God’s gifts and the diversity of those who receive them. The Church enjoys a multiplicity of peoples and cultures. Its members have different gifts, offices, conditions and ways of life. Within the Universal Church, there are particular churches that retain their own traditions. This great richness of such diversity is not opposed to the Church’s unity but rather adds to the miraculous nature of that universal quality.
At the Last Supper, Jesus prayed that his followers would be one and true to his desires, the Church has always struggled mightily to maintain unity. It has not been an easy task and throughout the centuries, from the first generation until the 21st century, there have been massive problems that presented themselves to the Church and attempted to undercut or dismantle its unity. These movements have caused tremendous pain and suffering but they would never destroy the unity of the Church. They hurt it, they lessened its effectiveness but the unity has always been there.
There are many ways in which these rifts tearing away at the universal unity of the Church can occur, but among the principal ones are heresy, apostasy and schism. I will come back to that in a day or so.