Dating back to classical antiquity, most philosophers thought that the universe had existed forever. Aristotle, as I mentioned, affirmed an eternal universe without a beginning in time.1 He argued that belief in a temporally finite universe entailed a logical contradiction. He thought of time as a series of connected moments, each with a beginning and ending, connecting to the beginning of the next moment and coming from the ending of the previous moment. If the universe began with the first moment in time, it must have come from the ending of an earlier moment.
