Recently I stumbled across a sticky note with some of my thoughts scrawled on it:
Fiat: a purposeful suspension of reality which gives the Affirmative team a degree of authority to execute their policy.
Since debaters don't have any real authority, we aren't congressmen by trade, we have to pretend like we do, otherwise the debate is totally meaningless and can't go anywhere. Negs would always win because, "AFF doesn't have the power to actually DO anything in the real world. Ergo, this discussion is fruitless."
Given proper limits, however, Hypothetical discussions can be extremely fruitful. Thus, we accept the arbitrary construct of fiat for the sake of fruitful discussion. The moment at which our discussion ceases to be fruitful because we've journeyed too far into the realm of the hypothetical is the moment at which fiat evaporates. The precise location of that line must be ironed out by the debaters in each round (or in each discussion with friends) and decided upon by the judge.
Understanding fiat isn't just helpful for debate. It's also useful in speculative discussions, especially political ones, which involve hypothetical situations. It allows you to analyze the discussion itself and make a decision about whether it has become fruitless because of wishful thinking. For example (not the best example out there): Suppose you're talking to your friend about nuclear weapons. Your friend asks, "Shouldn't everyone destroy their nukes to make the world a safer place?" Probably. Will it happen? Never in a million years.
Judgement call based on fiat analysis: They should, but they won't. End of discussion.
Thoughts? Additions? Corrections?