Where to now? Only the previously unknowable and unspoken will bring us there.

It frustrates and fascinates me that we'll never know for sure, that despite the best efforts of historians and scientists and poets, there are some things we'll just never know. What the first song sounded like. How it felt to see the first photograph. Who kissed the first kiss, and if it was any good.

Something was comforting about strangers—it seemed like they would exist forever as the same, unknowable mass.

Ralph Gomory, the President of the Alfred P. Sloan Foundation, proposes a tripartite division of science: the known, the unknown, and the unknowable. The known is taught in the schools and universities and is exhibited in the science museums. But scientists are excited by the unknown. Parenthetically, artists go to art museums to learn; scientists do not go to science museums because those museums act as if it's all known and preordained. That may be changing; exemplars are the Exploratorium in San Francisco and the American Museum of Natural History.

Gomory's tripartite division proposes three distinct areas: the known, the unknown which may someday become known, and the unknowable, which will never be known. The unknown and the unknowable form the boundary of science. Here are examples of questions for which the answers are today unknown.

I wanted to buy a T-shirt that read: I AM UNKNOWABLE.

Another person: a door you can't enter, even by knocking.