NEW YORK — Day-to-day, investigative reporting is about sweat and perseverance. Forget about the widely held view that government officials "leak" embarrassing stories to eager reporters who sit waiting for the phone to ring. You know — and I know — that hardly anything of value falls from the sky like manna from heaven. There is, however, something more important than tenacity. In the beginning, I would argue, it is not the work, but the idea, that is critical — a willingness to open our minds and look at things without preconceptions. What does this mean? For those of us privileged enough to ply our trade in democracies, the most dangerous form of censorship is the one we impose on ourselves. More often than many of us would acknowledge, we miss the truly amazing stories by circumscribing our reporting at the outset. We premise our inquiries on assumptions about how people would plausibly act. "No," we tell ourselves, "they would never do that." In fact, recent history is the chronicle of one implausible turn and twist after another. Who could have imagined that an American president with a commanding lead in the polls would join the conspiracy to cover up the burglary of his opposing party's headquarters?