General anesthesia doesn’t just work on your brain or on your mind. It works on your consciousness. By altering the delicate electrochemical balance within the neural circuitry inside your head, the basic ground state of what it is to “be” is — temporarily — abolished. In this process lies one of the greatest remaining mysteries in science, and in philosophy too.

Somehow, within each of our brains, the combined activity of billions of neurons, each one a tiny biological machine, is giving rise to a conscious experience. And not just any conscious experience, your conscious experience, right here, right now.