We seem increasingly to be living in 'interesting times' where our society is torn by division, instability and polarisation. It's an ugly period where lies have been legitimised, nastiness normalised, and rage has become routine. How should we as Christians react? There are certainly a number of inadequate responses.

The first inadequate response to the problems of our times is dismissal. So in Britain, for instance, it's not uncommon to hear statements like, 'Don't you worry. It'll pass over. We survived the Nazis and the Black Death.' The problem is disasters do happen. I wouldn't be surprised to find an archaeologist discover the equivalent of 'Keep calm and have a cup of tea' in the ruins of Pompeii. There is a spiritual form of this dismissal which is, 'God has his hand on this nation; don't you worry – it'll all be alright.' My trouble with this is it is exactly what a lot of people in the Old Testament said, only to find it ended up with a long walk to slavery in Babylon.

The second response, equally inadequate, is to react to the problems with despair. This is to survey all the problems and then with a weary sigh say, 'There's nothing we can do so let's just ignore it.' Again there is a sanctified version, which mutters darkly, 'Well we are in the last days, what can we expect?' Yet the fact is we are commanded to keep living in faith, hope and love until we are told to stop, and I, for one, haven't received that order yet.

The third inadequate response is to react to the challenges of our time by disengagement. Here we take a look around at the turmoil around us and tiptoe quietly away. We hope that by retreating tortoise-like into our shell we can escape the furore. The unspoken hope is that if we close the doors and keep busy then when we open them again we may find that the problem has gone away.

The result of a policy of disengagement is inward-looking Christians in inward-looking churches. Now there are lots of problems with this. It is of course a denial of the command that we have from Jesus to go into all the world. I'm reminded of the wise words: a ship in harbour is safe – but that is not what ships are built for. I imagine that this disengagement strategy goes down very well in Hell where the policy has always been that if you can't crush the church by persecution or render it useless by theological compromise, the next best thing is to contain it. After all, the inward-looking church of today is the empty church of tomorrow.

As an evangelist I find this response of disengagement to our troubled age particularly frustrating. You see I believe that, contrary to first impressions, this perplexed, fearful and angry time we live in is one of extraordinary opportunity for Christianity. Now before you question my sanity let me explain.

It's always tempting to be preoccupied with those spectacular issues that dominate the landscape of politics and national life. After all, these are matters that sell the papers, generate opinion polls and dominate conversations. In Britain at the moment it is Brexit, but there are similar matters in other countries. Yet let me suggest that to focus on these headline subjects is to mistake the effect for the cause, the symptom for the disease. The real problem – and people are beginning to sense it – is that the big issues of life have been ignored. There is a growing sense that much of the present disorder is quite simply due to the fact that as a society we no longer know who we are or how we are to live. We have lost the rulebook for the game of life.

The result is that although the term may not be used there is a 'great debate' going on. In it a vast number of questions are being asked. What should a nation stand for? What are the values that we should defend? Does truth actually matter? Is prosperity the ultimate value for a society? Should (or shouldn't we) welcome the stranger? Should the rich be allowed to get richer without any obligation to the poor? It's an utterly vital debate and Christians need to get involved in it.

The need for us to speak out wisely and deeply on the issues of our time is heightened because so many of the chattering prophets who happily promoted post-modernism, secularism, Neopaganism and a hundred other -isms have, at this moment of crisis, quietly absented themselves. They have nothing to offer and they know it. It's precisely at times like this that Christians need to preach God's wisdom and God's salvation in Christ. So whatever form the debate takes, let's not miss out on it. Whether at the workplace or coffee shop, we need to reject the temptation to go into disengagement mode and stay quiet. Let's seize the opportunity and stand up for God's truth!

There's a story, widely claimed to be about Oliver Cromwell: during a financial crisis in Britain, silver, the basis of the currency, was in short supply. When someone pointed out that there were large amounts of silver to be found in the statues of saints in the cathedrals, Cromwell made a bold suggestion: 'Let's melt down the saints and put them into circulation.' It seems to me to be a prophetic challenge for our time: let's get the saints out and get them into circulation!

Canon J John is an evangelist. Find him on Twitter @CanonJJohn