Or if you prefer a different metaphor, the body has randomly made hundreds of millions of different keys, or antibodies. Each fits a lock that is located on a pathogen. Many of these antibodies are combined such that they are alien genetic material—at least to us—and their locks will never surface in the human body. Some may not exist in the entire universe. Our bodies have come stocked with keys to the rarest and even unimaginable locks, forms of evil the world has not yet seen, but someday might. In anticipation of threat from the unfathomable, our defenses evolved as infinity machines.
