"And they'll know we are Christians by our love, by our love, yes they'll know we are Christians by our love."

So we sang in the late 1970s, in a culturally appropriate rock ballad idiom, and very real it seemed at the time. I came to faith in an evangelical Anglican tradition which had been shaped by the charismatic renewal movement and a key sign of this was an authenticity of relationships which had been absent from the starchy formality of much church life.

It was, in fact, a key part of my own coming to faith. As a struggling teenager in a large all-boys school, I was keenly aware of the competition to be accepted—to be cool—and also aware that I wasn't doing very well at it. By an odd series of 'coincidences', I met people from the youth group of the local Anglican church, and over about nine months decided that I wanted to be part of this Christianity thing.

For some time I had thought that what appealed to me about Christian faith was that it was well thought through, that it made sense. It was only when I had to tell my story some years later as part of a mission week in another church that I realised it was love that had made the difference. It was the acceptance of me as I was, without having to prove myself, that drew me to faith—and pointed to the loving acceptance of God.

As I look back, all this was very real—but it was also relatively easy. We were genuinely concerned for one another, but that wasn't difficult because we were mostly similar to one another. As I moved to new contexts and met new Christians, often from backgrounds quite different from mine, I learned something new about Christian love. Loving the other meant just that—loving people who were 'other' than me.

TRUE CHURCH

One of the hallmarks of true 'church' is that it includes people who would not otherwise associate together. If we meet to worship with people who we would like anyway, then it is not the love of God which has drawn us together. As Stanley Hauerwas has commented, "The kingdom of God is a party with a bunch of people with whom we wouldn't be caught dead spending a Saturday night had not we also been invited."

I recently heard a church leader talking about some of the tensions in their congregation between a judge who attended and ex-convicts who also came. The judge was finding it quite a challenge to worship alongside people that he had sent down! It's the kind of challenge that God's love poses us.

But it does not end there. Having learnt the importance of love over the years, and that true love means love of the 'other', I was stopped in my tracks a few weeks ago by a text I was due to preach on. I think it must be the most extraordinary verse in the New Testament, and it is one about love.

"My dear children, for whom I am again in the pains of childbirth until Christ is formed in you..." (Galatians 4:19).

Paul is saying something theological here; the image of the 'pains of childbirth' is an Old Testament metaphor for the sufferings of God's people as they await deliverance from their oppressors and freedom to worship God without fear. (There's a theological pun here—they are waiting to be 'delivered' from birthpangs!) For Paul, this deliverance has come to his people in Jesus, and each person experience the promised 'new creation' in him (2 Corinthians 5:17).

But Paul is also saying something profoundly personal. His love for these Christians is such that he is caused physical pain until they reach the maturity that is theirs in Christ. He is in pain and discomfort until they reach what he himself longs for—"the prize for which God has called me heavenward in Christ Jesus" (Philippians 3:14).

I think I have learned to love people, even people quite different from myself. But to so long for the best for others that I am in pain until they have attained it? That is another whole kind of love. It raises the bar way above anything I have reached. It is a love that might change the world—but I am very clear that it is a love I cannot work up in myself. It is a love that must be the gift of grace from God, formed in my by his Spirit. Maybe it's just the kind of love by which "they'll know we are Christians..."

Rev Dr Ian Paul is associate minister at St Nic's, Nottingham, and Honorary Assistant Professor at the University of Nottingham. He blogs at www.psephizo.com and tweets at @Psephizo.