Rebecca Jones, in a recent post, appeared to be portraying Jesus as a sort of first-century Jeremy Corbyn – an uncompromising idealist for whom the world’s problems were largely the result of betrayal of principles.

For those of us who don’t feel wholly easy about Corbyn, but do claim to follow Jesus, that poses a dilemma.  And it is a dilemma which is at the heart of contemporary theological and political thinking.

Of course the world needs idealists. If it had not been for the drive of the Green movement (Rebecca also mentions Natalie Bennett), would we have got the Paris climate change agreement, a dramatic and game-changing moment in human history despite all the uncertainties about its implementation? And if it were not for the insistence of Jesus that love and forgiveness must have the last word, would the human race as a whole – non-Christian as well as Christian – show even the limited level of generosity which is needed for everyday life to function effectively? Who knows?

But everyday life cannot be run on love and forgiveness alone. Jesus was not a politician (though his replies to those who challenged him could be amazingly politically canny). He did not offer to guide us through the practicalities of day by day living in society, still less the world of economics. After all, the Jews had a scripture, evolved over centuries, very diverse in its approaches to the business of living, but giving plenty of clues about those practical issues. Jesus took all that as read, and challengingly went beyond it to the “impossible possibilities” of a yet better way of life. We however, starting with those first Christians, have to live in the continuing everyday. And we often have to look to sources additional to the Gospels if we need guidance.

The late Reinhold Niebuhr remains, for my money, one of the greatest social/political theologians of recent times, perhaps of any time. “Christian realism” was his watchword. Too conservative for the liberals, and too liberal for the conservatives (in both theological and political senses), he steered a practical path through the great issues of the mid-20th century, from the New Deal to the Cold War. He saw excessive idealism and utopianism as positively dangerous in a world where self-centredness was endemic and all power tended to corrupt. He thus refused to read practical principles straight across from Jesus and the Gospels, though he consistently maintained belief in the “impossible possibility” (his own phrase) of the Kingdom of God.

As one who has lived in the “shades of grey” of the British Civil Service, with its genius for compromise, I invariably found Niebuhr’s approach rang true for me. No doubt he was not always right; who is? But his approach seemed more authentic, in my situation, than that of those idealists – be they evangelical, charismatic, catholic or liberal – who simply present “Jesus only” as the rule, and the Kingdom portrayed in the Gospels as the sole way of living.

Dietrich Bonhoeffer died for his anti-Nazi principles, and is surely a candidate for one of the 20th century’s more Christ-like figures. Yet he too was a hard-nosed realist in many ways. “We hope for the Last Things, but believe in the next-to-the-last” was how he summed it up. Wrestle with the things of this world rather than trying to take a short cut to the Kingdom.

That Kingdom, which the Church preaches in Advent – the ideal state of things, post-Jesus, post-Corbyn – is in the strictest sense inconceivable. That does not mean that it is not real, nowhere present, never going to happen. It simply means that this vision cannot be our only guide to practical politics.

The French people, including many left-wingers, have just voted in large numbers to support conservative Assembly candidates in order to keep out the Front National. Shock horror! Betrayal of principles! What would Jesus (or Jeremy) do? We only have to ask this to realise that the question is meaningless. We follow a vision, yes - without vision, the people perish. And there is much in Jesus’ vision, and those of other idealists too, which necessarily challenges us. But we make our decisions according to the realities of our own situation.

If religious and political groups alike could accept that that is how human beings must live together, rather than being guided solely by idealism, the world would be a healthier place.