In these situations, it is only a matter of time before something triggers me into refuting a comment that they make to comfort each other. This evening the first one related to the doubt that a non-believer could ever truly forgive. The clinching comment was that the word 'forgiveness' has been misappropriated by the secular community. This seemed to be an ideal opportunity to strike.
Armed with a good catalogue of stories about altruism among the great apes, and challenging my guest about the use of the term 'misappropriation', I gently but assertively suggested that it might be the other way round. He did at least have the decency to admit that he didn't actually have any evidence for his original claim, and kept retreating into the refuge of semantics. Fortunately his wife - sensible lady - then pounced on him too.
A later discussion about the meaning of the term 'secularism' demonstrated that they regard it as a threat to Christianity too. When will they learn that secularists are not attacking Christians but only defending the right of everyone not to be bullied by any particular religion?
Outnumbered four to one, I felt that I defended my position adequately, although not expertly. It would be nice to imagine that something I said might sow the seeds of questioning and doubt, but I know it won't.
I'm sure they will come to dinner again.