Image credits

Portraits come from Wikimedia Commons.

• Arthur Schopenhauer — Photograph by Johann Schäfer, 1859 · public domain
• Plato — Bust after Silanion, Musei Capitolini · photo Marie-Lan Nguyen, CC BY 2.5
• Aristotle — Roman copy after Lysippos, Palazzo Altemps · public domain
• Marcus Aurelius — Bust, Glyptothek Munich · public domain
• Friedrich Nietzsche — Photograph by Gustav Schultze, 1882 · public domain