The Renaissance doctor Paracelsus stressed the vital importance of the dose. “All substances are poisons; there is none which is not a poison. The right dose differentiates a poison.”

This is usually taken to refer to medicine but it could also, I’ve been thinking, apply to poetry. Poetry, as Keats and others have argued, is itself one of the world’s greatest and most potent medicines, though scandalously underused and underprescribed.