On April 11, 2020, John Horton Conway died of COVID in a hospital in New Brunswick. He was eighty-two. The newspapers wrote: “The mathematician who invented the Game of Life has died.” His colleagues wrote: “One of the greatest minds in combinatorics has died” — the science of how many ways you can rearrange, connect, and count things that, seemingly, don’t need counting. Both were right — and both missed the point. Because Conway didn’t “invent a game.” Conway showed that from four rules you can build a universe — and that the universe won’t notice it’s built from four rules. From the inside, it will look like the real thing.