This is the script of this morning’s Thought for the Day on BBC Radio 4’s Today programme.

I live not far from Haworth, home of the Bronte sisters. The youngest, Anne, was born two hundred years ago today. One line from her writing stands out for me: “He who does not grasp the thorn should never crave the rose” – which is a bit more poetic than “Get stuck in, whatever the cost.”

This is the sort of notion that hit me when I was out in Sudan last year, speaking at a diplomatic conference on freedom of religion and belief at a time of protest and instability there. Meeting with protesters, academics and lawyers, it became clear that they held a variety of views on how a future Sudanese society should be shaped. They were united in wanting freedom and justice, but that unity got thorny when conversation got onto detail and process.

Of course, the other thing they had in common was a willingness to put their body and life where their opinions and convictions lay. So many of the Sudanese people I knew there shared this understanding: that opinion has to be backed up with action, and action might incur a cost.

After this week in Khartoum I went to Jena in Germany. On arrival I was asked to take part in the dedication of a memorial to the young German theologian and pastor Dietrich Bonhoeffer at Buchenwald Concentration Camp near Weimar. Bonhoeffer was hanged a month before the end of the war. For him, theology was not a matter of an internal world of vague spirituality; rather, it involved discerning the character and call of God in the real world of the Third Reich and then committing himself to its consequences. Put crudely, if human beings are made in the image of God, then destroying them is not on.

It is this element of commitment that appears to be absent from much of what passes for debate in the ‘any dream will do’ generation. The vision I have for people and society must demand of me the sort of action and commitment that must in turn cost something.

When I read the gospels, this screams out of every text. It’s why the child Jesus argues with the theologians in the Temple; why he stands silently in front of Pontius Pilate, questioning who is actually being judged and where power really lies; why he never sweetens the vocational pill, but tells people that if they do choose to come and walk with him, then they’ll probably share his fate. No illusion, fantasy or seduction – just reality. Don’t crave the rose if you aren’t prepared first to grasp the thorn.

It seems to me that today every opinion is valid. But, I suggest, the only ones worth taking seriously are those that cost.