So who was the greatest mariner of the 15th century? Well, as usual, it depends on your definition of greatness. If you value administrative competence over ill-advised adventure, then Zheng He is certainly the winner. But the reason we remember Columbus over him or Vasco de Gama is that Columbus' voyages had a lasting impact on the world, even if it wasn't necessarily a positive one. And that makes me wonder what kind of person you'd want to be. A capable administrator and brilliant sailor like Zheng He, a daring captain like de Gama, or the bearer of a complicated but famous legacy like Columbus? Let me know in comments.