It is timely, in these days of Extinction Rebellion and anti-aviation protests, to examine the philosophy of travel. Why do we go, what do we get out of it, and is the very act of boarding a plane nefarious? As Emily Thomas asks in this searching book, ‘Is it ethical to visit the Great Barrier Reef if its corals are withering?’

An academic at Durham University, Thomas explores the places where philosophy and travel intersect. She specialises in the history of philosophy and has written on 17th-century theories of time. ‘Philosophers Abroad’, which is the subtitle of this slim-ish volume, is a nebulous enough phrase, but the author makes it her own.

There is a myth that philosophers never travel, says Thomas. It’s true that Socrates did not step beyond the city walls of Athens and Kant never ventured more than a hundred miles from his birthplace. But many philosophers have thought about the subject. Montaigne’s 1580 Essays, for example,