What good is a canon? It's a question that hovers in endless debate near cinephile culture. The idea of distilling cinema down to its "best" or "most essential" films is like a game or a thought experiment, and whether it be the AFI or Sight & Sound or a group of Young Turks looking to rattle conventional wisdom, canon-making demonstrates nothing so much as a desire to assemble an expansive, fragmented, and still-evolving sense of film history into some sort of definitive order. Canons, each with its own biases, are useful chiefly as a starting point or a basecamp. The best answer is to always be looking, always curious. And cinema has barely more than a century to keep up with. I wonder how bibliophiles cope.One of the virtues of the San Francisco Silent Film Festival, which begins on May 28th, is how it mixes classics and arcana on a level plane.