What is a Christian? What is a Catholic?

I went out for supper with a good friend recently, and we had a very interesting (and quite extended) conversation about all things religious. I wish I had taken notes, because we covered a lot of ground. One part of our conversation that particularly grabbed me was the question "What is a Christian?", quickly followed by "What is a Catholic?"

A Christian is a person who places his or her faith in God through Jesus Christ. The earliest and most fundamental creed of the Christian is "Jesus is Lord", which is found in several places in the New Testament (such as 1 Corinthians 12: 3b - "No one can say 'Jesus is Lord' except by the Holy Spirit.") This is a lot stronger than it sounds. "Lord", or in Hebrew "Adonai", was a term used to refer to God Himself. This simple creed already starts to imply that Jesus has a divine nature. It also implies that just as there is only one God, there is only one Lord par excellence, and that is Jesus.

A Catholic is a Christian whose faith is lived in a concrete historical community (a "church") which lives in communion with St. Peter and his successors i.e. the Bishop of Rome, a.k.a. the Pope. There are lots of churches out there. What sets the Catholic church apart from the others is that this particular church lives in communion with the Pope. Catholics do believe that other Christians truly are Christians, but also believes that the function of St. Peter (and his successors) as a centre of unity is part of the will of God for the Church. For this reason, Catholics believe that the fullness of the reality of the Church subsists only in the Catholic church, without denying the authentic status of other baptized people as Christians.

Obviously these are more "spiritual" than "sociological" answers. I bet there are a lot of people who write "Catholic" on the census form who are not, in fact, living in communion with the Pope. I bet there are a lot of people who self-identify as "Christian" for whom Jesus is not really the Lord. But very few of us are perfect believers just yet. Very few of us have totally turned over every aspect of our lives and will to Jesus just yet. The real danger as I see it is spiritual complacency, and presumption. As long as people are still journeying, God can still sneak in with his grace. We just need to be willing to be challenged, and to be called to self-consistency with our faith and our life.