Shortly before his arrest, Jesus prayed for unity among his followers, those with him then and those who would come after: us, the church of today. His prayer was that we would be one in him, show each other the deep, unconditional, sacrificial love he has shown us, and that this love would show the world God's very nature (John 17:11-24).

Unity and love. They seem like simple words, with plain meanings. And yet, sometimes what we mean by unity is actually an unhealthy and superficial show of pleasantness. And sometimes what we mean by love is the avoidance of confrontation.

Here are three factors to bear in mind before we weigh in on a robust Facebook discussion or shame those expressing disagreement...

1. Supressed disagreement is not unity

What Jesus had in mind when he prayed his people would be united was not that they would never ask each other difficult questions, or challenge each other's beliefs on important issues, or even that they would stick together regardless of difference. Unity is not unity when it is a façade hiding deep fractures. Some of the disagreements raging in the church today need to be worked through. They concern the most fundamental aspects of our faith: who is God? How does he reveal himself? What does he require of us? There are some things we can all agree to disagree on, trusting each other to come to our conclusions before God and in community, but sometimes we need to have painful debate. And some things, dare I say it, may be important enough to divide us. Unity for unity's sake is meaningless.

2. Buried conflict turns toxic

If we don't engage honestly with one another, however painful this may be, the church will drift apart and passive aggression will poison us. In her book Fierce Conversations, the American executive coach Susan Scott argues that unless we take the risk of expressing what is on our minds and hearts, our relationships will die. She writes: "The conversation is the relationship... If we lower the standards about how often we talk, what we talk about, and, most important, the degree of authenticity we bring to our conversations – it's a slow and deadly slide." Conflict feels threatening and dangerous, but it is just as dangerous to ignore what needs to be aired.

3. There is a difference between personal attack and critical engagement with ideas

I have to put my hands up and confess here I find it terribly hard to have discussions about beliefs and ideas without taking critique of my position personally. So I say this to myself as much as to anyone else: it is vitally important that we learn to debate, to wrestle with complex arguments, and to stay present in painful discussions around important issues, however threatening we might find them. I've recently come across Dr Marshall Rosenberg's work on conflict and mediation. His book, Nonviolent Communication (Puddledancer Press, 2003) has been hugely influential and its principles are taught in war-torn areas around the world to this day. If, like me, you struggle in this area, I would highly recommend getting hold of this book as a good place to start.

What could possibly be wrong with calling for Christians to down weapons and cluster together, united before a fractured world? Nothing, I'd argue, so long as we don't use the concept of unity to shut down the expression of righteous anger, robust mutual critique, grief and honest engagement around painful issues.

If we remain in God's love and strive to show this same love to each other even as we wrestle over disagreements, we have nothing to fear: "There is no fear in love. But perfect love drives out fear." (1 John 4:18)