Beyond Weird

by Philip Ball

David Hume argued that we can never be certain about interpreting causation. If we find that A seems invariably to be followed by B, we might infer that A causes B, but that inference can’t be proved correct. In Critique of Pure Reason (1781), Immanuel Kant went further, saying that we have no access to the world that is not mediated by experience.

All of the photons of sunlight that bounce off the moon are agents of decoherence, and more than adequate to fix its position in space and give it a sharp outline. The universe is always looking.