Ah, in that case I apologize for miscommunicating. By 'strictly correct' I meant 'literally, objectively true in the context of the story.' Whether Harry's goal is in fact possible most likely won't be revealed for quite some time; spilling the beans now wouldn't be dramatic. But, by the same token, it's not (yet?) knowably false.

I agree that Harry is being extremely, perhaps excessively, confident about something he can't really prove, and that such behavior is risky. However, it's an acceptable sort of risk, since he can always find contrary evidence later and change his mind, do something else with the rest of his life. The sort of risk entrepreneurs take. He hasn't hit any self-modifying point-of-no-return.