Toward the end of his life, the great 20th-century physicist John Archibald Wheeler proposed an idea he called "it from bit": The universe, he claimed, isn't ultimately composed of matter and energy, or fields and forces, or space and time, but instead, digital bits of information. Scientists have been intrigued by this conjecture for decades, but no one has known where to start building such a radical theory. The Simplest-Case Scenario is a tour of physics and philosophy with stops at relativity, quantum mechanics, the multiverse, probability, chaos theory, fractals, the Big Bang, the origin of life, and human and animal consciousness - leading to a unified picture in which the Cosmos is far, far simpler than we think. Based on a prize-winning physics essay.