Spirit is a breath. The Latin spiritus meant the air in your lungs before it meant anything holy, and the same is true almost everywhere you look — the Greek psyche, the Sanskrit prana, the Hebrew ruach. To the ancients, breathing and being were the same act, and the words still know it even though we've forgotten.
This is the strangest archive of all: the words for our own insides. When people first reached for a name for the soul, they didn't invent something new. They pointed at the most ordinary miracle they had — the breath that came and went and one day didn't — and said, that, that's the part that matters.
I find I can't say inspire, or expire, without hearing the breath inside it. Inspire is to breathe in. Expire is to breathe out, for the last time. The body wrote the dictionary of the mind, and the mind has been pretending otherwise ever since.
These are the word origins of being human — the etymology of breath, soul, heart, and the thin line we draw between body and mind. They record a time before that line existed, when to lose your breath and to lose your spirit were not two events but one.
We've built whole sciences on the assumption that the mind is one thing and the meat another. The oldest words disagree. They keep insisting, every time we say them, that the soul was just the air — and that we are, all of us, only borrowing it, on the long exhale we mistake for a life.