The text around the edge is the final passage from Austrian philosopher Ludwig Wittgenstein (1889 –1951)’s Tractatus Logico–Philosophicus: ‘My propositions serve as elucidations in the following way: anyone who understands me eventually recognises them as nonsensical, when he has used them – as steps – to climb up beyond them. (He must, so to speak, throw away the ladder after he has climbed up it.) He must transcend these propositions, and then he will see the world aright. What we cannot speak about we must pass over in silence.’