Reply #6: It's essentially saying that the only type of time travel allowed

[Salviati]

is the history fulfilling type of time travel. The kind where you can go back in time and do things, but only because that is what you've done already. This is the kind of time travel in "12 Monkeys", as opposed to the kind of time travel where you can change events that have already taken place, i.e. like "Back to the Future"