In 1880, the French government commissioned a young sculptor named Auguste Rodin to create a pair of bronze doors for a planned Museum of Decorative Arts in Paris. The theme: Dante's Inferno. Rodin spent the next 37 years obsessively working on it. The museum was never built. The doors became something else.

The Gates of Hell, as they came to be known, were six meters tall, covered in 180 writhing figures. At the top, above the chaos, Rodin placed a seated man — nude, muscular, leaning forward with his chin on his fist. Originally called 'The Poet,' the figure was meant to be Dante himself, contemplating the torments he's about to describe.

But Rodin noticed something. Cast on its own, removed from the doors, the figure stopped being Dante. It became a universal image of thought itself. He enlarged it to life size, then monumental. By 1904 it had a new name: Le Penseur. The Thinker.

It's now the most reproduced sculpture in history. Museums have over 20 authorized bronze casts. The silhouette has been parodied millions of times. Nobody needs to be told what it means.

The Gates of Hell itself was never finished as a functional door. When Rodin died in 1917, the full composition existed only as a massive plaster study. It was cast in bronze decades later, posthumously. You can see it at the Musée Rodin in Paris — and if you look carefully at the very top, above all the damned souls, there's a miniature Thinker, staring down exactly where Rodin first placed him.

The universal symbol of human contemplation was, originally, a man looking at Hell.