If you're reading this, you know what living looks like - movement, neurological activity, thought, action.
But what exactly is death?
The answer is complicated, suggests neuroscientist Christof Koch. In "Is Death Reversible?" a feature article in the most recent issue of Scientific American, Koch grapples with a death definition that is much more nuanced than you might think.
"Death, this looming presence just over the horizon, is quite ill defined from both a scientific as well as a medical point of view," he writes.
Koch tracks a shifting concept of death, from the cessation of breathing to the end of brain activity. And, he suggests, the modern medical definition is being shaken by new scientific developments.