I realise that he has the notion that darkness is a substance. It will make you choke if you swallow too much in one go. I could have put him straight with some prosaic account of the coughing reflex. But I didn't. I stashed away the treasure of the image, and left him with the version of reality fashioned by his own infant brain.
Reality is under constant review.
The function of the brain, he thought, was to cool the blood. He built his cosmology on the belief that the earth stands motionless at the centre of the universe. He was utterly wrong on each count, but his beliefs served him well enough. And although we now know immeasurably more than Aristotle about the body and the structure of the cosmos, we should not delude ourselves by thinking that we have arrived at some endpoint of intellectual evolution. We still live by intuitions and illusions, especially when our thoughts turn inward.