Human

The body is the tangible half of a person, an intricate arrangement of nerves, organs, blood vessels, bone, and muscle tuned to deal with its surroundings. It obeys the same natural rules as the planet's other animals, differing by species yet built on a shared plan. Chemically, one human body works out to roughly 35 liters of water, 20 kilograms of carbon, four liters of ammonia, plus lime, phosphorus, salt, saltpeter, sulfur, fluorine, iron, silicon, and faint traces of fifteen further elements.

Set against the body is the soul, sometimes called the spirit, which the series treats as belonging to humans alone. Incorporeal and seemingly undying, it holds a person's sense of self and every feeling, breaks away from the flesh at the moment of death, and carries enough raw energy to drive human action and even fuel certain transmutations. Binding the two together while a person lives is the mind; so long as body and soul both survive, however battered, that link pulls them toward one another, straining to rejoin. Their reasoning and their souls also let humans recognize each other beyond mere biology, so they tend to band together and even gamble their own lives for someone else rather than simply fighting to outlast one another.

What counts as a human normally follows a familiar checklist, but alchemy complicates the label. As the craft advanced and experimenters began reshaping people through it, the neat definition frays, above all for anyone whose body or soul has been warped, damaged, or rebuilt, which leaves open the question of where being human really ends.