Some years back, I came upon my husband’s old criminal law text and started to read it. One of the cases that caught my eye concerned shipwrecked sailors, and the surrounding discussion touched on an unsettling thought experiment proposed by an ancient Roman philosopher named Carneades. It goes like this:

Two drowning sailors find a plank floating in the water, but the plank can only support one. Sailor A arrives at the plank first, but B pushes him off and is later saved. Is B guilty of murder, or is the concept of necessity a particular kind of self-defense? And if it isn’t, is Sailor B’s only moral course of action to quietly die?

Soon after, the character of Grace Winter came to me and started defending herself—for what, I didn’t immediately know. When I started writing, I knew only that Grace had survived a shipwreck and that she was on trial for her life, things the reader finds out in the first chapter of the book.

I have always been intrigued by how the law tries to tell a story in a way that allows us to judge it—to decide who’s innocent, who’s guilty, and who goes to jail. I wanted to write a story that shows how hard it is to judge people for things they do in situations we have never faced, and maybe never even contemplated.

Carneades’s thought experiment highlights how the fundamental human conflict is between man and nature and how all other conflicts stem from that. It’s easy to see that resolving such conflicts takes on added urgency in a world of growing population and shrinking resources, so maybe The Lifeboat is partly about that. But most of all, it is about a young woman who keeps having to save herself, something we are all doing in various ways every day of our lives.