Nothing in particular happened to either of them; the clergyman was not in the seer's mind at the moment.
This is a good example of a solitary hallucination in the experience of a very cool-headed observer.

The _causes_ of such experiences are still a mystery to science.

Even people who believe in "mental telegraphy," say when a distant person, at death or in any other crisis, impresses himself as present on the senses of a friend, cannot account for an experience like that of the diplomatist, an experience not very uncommon, and little noticed except when it happens to coincide with some remarkable event.

{56b} Nor are such hallucinations of an origin easily detected, like those of delirium, insanity, intoxication, grief, anxiety, or remorse.

We can only suppose that a past impression of the aspect of a friend is recalled by some association of ideas so vividly that (though we are not _consciously_ thinking of him) we conceive the friend to be actually present in the body when he is absent.
These hallucinations are casual and unsought.