Sawyer freaks out banging on the Swan station door

Sawyer has a bit of a meltdown banging on the Swan station door, trying to get someone to answer. This prompts Daniel Faraday to explain one of the rules to Sawyer. Apparently, since Sawyer met Desmond after he left the hatch, it's not possible for them to meet earlier than that. These rules are really confusing, yet very interesting.