I am a Catholic priest, but got ordained rather later than is usual, because first I was a Protestant pastor. I was born and brought up in a Protestant family, and wanted sincerely to serve the Lord as a minister. Before going on to study theology, however, I went abroad for a time straight from university to work in West Africa. I found a good Christian community there and was happy, but for the first time I was struck by all the different churches and the innumerable African sects that had sprung from Protestantism.
Look around you and leave out the word "African", and you will see the same thing - endless groups, large and small, each depending on their own leader, all disagreeing with one another, often violently.
All right, you can say, but they are united in believing that Jesus is Lord. Yes, I suppose they are, but what sort of unity is that, where they cannot even worship God together? Would you think a family was united if each person clung to his own ideas, claiming that he was right and everyone else was wrong, and they would not even meet for meals? Would you want your son or daughter to marry into such a family?
Don't ask me why that first came to me there in Africa and not earlier in England. I don't know. Perhaps it was the work of the Holy Spirit, but anyway, it shook me. For the first time, also, I was in a country where the majority were not Christians and for the first time I had stepped outside my own little Church and was looking at Christians from outside, and thinking, "What is all this?"
I went back and studied theology and got ordained. But that doubt never left me. The more I studied, the more I realized that for the first thousand years of Christianity there was only one Church - the Catholic Church, and that one Church that copied the Scriptures by hand and passed them on, only one Church united in one faith, and teaching with one authority under the guidance of the Holy Spirit.
The multiple churches and sects all sprang from the Protestant Reformation. Once approval and impetus had been given to private judgment (against what the Bible teaches us), Christians went on and on spreading division and confusion. (I am not talking about the Orthodox Church, because that case is historically quite different, and, anyway, the beliefs of Catholics and Orthodox are more or less identical.)
It seemed to me that the only Christians who could claim to go back to Christ and who had been teaching with the authority of one voice were Catholics. In your own country you might belong to what you think is an old Church, but that Church will never be more than a few hundred years old (more probably it will no more than just a few years old). If you leave your country, you may find a similar group of people, but they will not be united with your church at home. Only the Catholic Church can be found in all places. Only the Catholic Church teaches with one voice and, wherever you are in the world, draws you to the one table fellowship, the Holy Eucharist. It does not belong to any nation or any continent or any race. It is the People of God,
We are human beings. We cannot claim to be united with each other unless we share each other's lives, and unless we belong to one "organization". That is just a fact of the human state. We have bodies, not just souls, and in our bodies and minds we belong together. You cannot claim to be "spiritually" married to someone. You have to married legally, physically, before it makes any sense in human society. I think the same thing about the Church. We have to belong together in a visible, physical way, not some sort of "spiritual" way which does not require commitment to each other and obedience to some higher authority than my own ideas and prejudices.
That is why I became a Catholic - because I wanted truly to belong to the Church which from the beginning, from the time of Jesus Christ, contains all that Christ wanted to give to his Church, and all the means and helps of becoming the Christian that he intends, the only way, I believe, of being a human being truly made in God's image.