Sum. David Eagleman

As you step into the street, you note there are no crowds, no buildings teeming with workers, no distant cities bustling, no hospitals running 24/7 with patients dying and staff rushing, no trains howling into the night with sardined passengers on their way home. Very few foreigners.

      You begin to consider all the things unfamiliar to you. You’ve never known, you realize, how to vulcanize rubber to make a tire. And now those factories stand empty. You’ve never known how to fashion a silicon chip from beach sand, how to launch rockets out of the atmosphere, how to pit olives or lay railroad tracks. And now those industries are shut down.

      The missing crowds make you lonely. You begin to complain about all the people you could be meeting. But no one listens or sympathizes with you, because this is precisely what you chose when you were alive.

       Descent of Species

      In the afterlife, you are treated to a generous opportunity: you can choose whatever you would like to be in the next life. Would you like to be a member of the opposite sex? Born into royalty? A philosopher with bottomless profundity? A soldier facing triumphant battles?

      But perhaps you’ve just returned here from a hard life. Perhaps you were tortured by the enormity of the decisions and responsibilities that surrounded you, and now there’s only one thing you yearn for: simplicity. That’s permissible. So for the next round, you choose to be a horse. You covet the bliss of that simple life: afternoons of grazing in grassy fields, the handsome angles of your skeleton and the prominence of your muscles, the peace of the slow-flicking tail or the steam rifling through your nostrils as you lope across snow-blanketed plains.

      You announce your decision. Incantations are muttered, a wand is waved, and your body begins to metamorphose into a horse. Your muscles start to bulge; a mat of strong hair erupts to cover you like a comfortable blanket in winter. The thickening and lengthening of your neck immediately feels normal as it comes about. Your carotid arteries grow in diameter, your fingers blend hoofward, your knees stiffen, your hips strengthen, and meanwhile, as your skull lengthens into its new shape, your brain races in its changes: your cortex retreats as your cerebellum grows, the homunculus melts man to horse, neurons redirect, synapses unplug and replug on their way to equestrian patterns, and your dream of understanding what it is like to be a horse gallops toward you from the distance. Your concern about human affairs begins to slip away, your cynicism about human behavior melts, and even your human way of thinking begins to drift away from you.

      Suddenly, for just a moment, you are aware of the problem you overlooked. The more you become a horse, the more you forget the original wish. You forget what it was like to be a human wondering what it was like to be a horse.

      This moment of lucidity does not last long. But it serves as the punishment for your sins, a Promethean entrails-pecking moment, crouching half-horse halfman, with the knowledge that you cannot appreciate the destination without knowing the starting point; you cannot revel in the simplicity unless you remember the alternatives.

      And that’s not the worst of your revelation. You realize that the next time you return here, with your thick horse brain, you won’t have the capacity to ask to become a human again. You won’t understand what a human is. Your choice to slide down the intelligence ladder is irreversible. And just before you lose your final human faculties, you painfully ponder what magnificent extraterrestrial creature, enthralled with the idea of finding a simpler life, chose in the last round to become a human.

       Giantess

      The afterlife is all about softness. You find yourself in a great padded compound. Everything appears designed for quietness and comfort. Your feet fall silently on the cushioned floor. The walls are pillowed. Echoes are dampened by foam ceiling tiles. A hard surface is impossible to find; feathers pad everything.

      When you enter the grand hall, the first thing you notice is a sizable and princely man. He looks just as you might expect a god to appear, except that he is noticeably skittish and strained with worry around the eyes. He will probably be explaining that he is greatly disturbed by the nuclear arms proliferation on Earth. He says that he often awakens in a cold sweat with the sounds of colossal blasts hammering in his ears.

      “To be clear,” he says to you, “I am not your God. Instead, you and I are galactic neighbors; I am from a planet associated with the star you call Terzan Four. So we are all in the same mess.”

      “What mess?” you ask.

      “Please don’t talk so loudly,” he softly admonishes. “For a long time we have been studying our neighbors: you Earthlings and thirty-seven other planets besides. We have developed highly accurate systems of equations to predict the future growth and social directions of your planets.” Here he fixes your eyes. “It turns out that you Earthlings are among the least tranquil and content. Our predictions indicate that your weapons of war will grow increasingly loud. Your space exploration programs will produce thousands of noisy vessels that will thunder throughout the heavens with their deafening rocket propulsion. You Earthlings are like your explorer Cortez, standing atop a mountain peak and preparing to perturb every beach at all the lapping fringes of the Pacific.”

      “We’re in a mess of expansionism?” you manage.

      “That’s not the mess,” he hisses. “Allow me to illustrate the larger picture. You and I, our planets, our galaxy—we’re part of what you should think of as an immeasurable living mass. You might call it a Giantess, but summarizing the concept in a word might give you the illusion that you can have a hint of a notion of her enormity.

      “To give you a sense of scale, you are the size of an atom for her. Your Earth—sprouting with its untold layers of furiously fecund species—your Earth is tantamount to a single protein in the shadowy depths of a single one of her cells. Our Milky Way constitutes a single cell, but a small one. She consists of hundreds of billions of such cells.

      “For millions of years, my people had no notion of her, just as a flatworm is unlikely to discover that the planet is round; a colony of bacteria will never know the walls of the flask; a single cell in your hand will not know it is contributing to a concerto on the piano.

      “But with advancing philosophy and technology, we came to appreciate our situation. Then, a few millennia ago, it was theorized that we might be able to communicate with her. It was proposed that we might decipher her structure, deploy signals, influence her behavior in the manner that infinitesimal molecules—hormones, alcohols, narcotics—influence a creature like you.

      “So we organized and educated ourselves. Instead of fretting through the doomed ignoble cycles of local politics, we dedicated our economy and sciences toward understanding the biochemistry of universal scales. We methodically mapped out the signaling cascades and stellar anatomy of her nervous system, and at last discovered how to transmit a signal to her consciousness. We sent a sharply defined sequence of electromagnetic pulses, which interacted with local magnetospheres, which influenced asteroid orbits, which nudged planets closer and farther from stars, which dictated the fate of lifeforms, which changed the gases in the atmospheres, which bent the path of light signals, all in complex interacting cascades we had worked out. Our calculations told us that it took a few hundred years for the transmission to arrive at her consciousness. At the time of the Arrival, I was sad to be traveling away from the planet while everyone was so excited to see what would happen.”

      His face twitches with painful trickles of reminiscence.

      “But no one would have guessed what happened next: a great sheet of meteors rained down, incendiary hydrogen clouds crushed in, and these were followed by a multitude of black holes that mercilessly swallowed up the flying chunks and dust and the last light of remembrance. No one survived.

      “In