The doctrine of eternal recurrence is Nietzsche’s most profound and most troubling teaching. It states that all events in the universe repeat infinitely in exact detail. Every moment you have lived, you will live again, and again, and again, forever. Your life does not happen once in linear time. It happens infinitely in cyclical time. The same choices, the same experiences, the same suffering and joy, repeated without end, without variation, without escape. Nietzsche presents this as both cosmological claim and psychological test. Whether the universe actually operates this way matters less than how you respond to the possibility. Could...