Robert Macfarlane is an explorer and linguist of landscape. His newest book, “Underland: A Deep Time Journey,” is an odyssey that’s full of surprises — from caves and catacombs under land, under cities, and under forests to the meltwater of Greenland. “Since before we were Homo sapiens,” he writes, “humans have been seeking out spaces of darkness in which to find and make meaning.” Darkness in the natural world and in human life, he suggests, is a medium of vision and descent, a movement toward revelation.

Robert Macfarlane is a reader in literature and the geohumanities at the University of Cambridge. His books include “Mountains of the Mind,” “The Old Ways,” “Landmarks,” “The Lost Words,” and, most recently, “Underland: A Deep Time Journey.”

Find the transcript for this show at onbeing.org.