One of the great intellectual puzzles that daily life forces all of us to consider on a slightly too regular basis is: ‘Why are other people so awful? How come they are so unreliable, aggressive, deceitful, mean, two-faced or cowardly?’ As we search for answers, we tend quite naturally to fall back on a standard, compact and tempting explanation: because they are terrible people. They are appalling, crooked, deformed or ‘bad’; that’s simply how some types are. The conclusion may be grim, but it also feels very true and fundamentally unbudgeable.

However, when things feel especially clear cut, we may be goaded to try out an unusual thought experiment, which stands to challenge a great many of our certainties and render the world usefully more complicated: we can try to look at our fellow humans through the eyes of love....