The Symmetry Objection to an Infinite Past

Present effects exist because of past causes, not future causes. The symmetry is broken when we see that in classical causation, causation flows in one direction, from the past into the future. If you started today and built one room of Hilbert's Hotel every year into an endless future, there would never be a time when an impossible hotel exists. This captures the essence of Craig's objection that an endless future is potentially infinite. It is potentially infinite if each moment involves actualizing something as part of a collection like incrementally building a hotel.