Sometimes we can discern a person’s thoughts, emotions, mood or intentions, or all of these, from a subtle clue. The great classical actor Ian McKellen illustrated this in a one-man performance on Broadway in the 1980s. While explaining how an audience can pick up on the slightest onstage movement, he produced a slight twitch just below his left eye. The movement was obvious to everyone in the house, which immediately responded with laughter. The twitch of a single muscle had given everything away. We in the audience may not have been transcendent but McKellen was, and is, in his craft.

Subtlety is akin to precision and incisiveness. It is the delicate art of being certain, and correct, on the basis of a tiny clue.