It's really just short hand for rationalist debate in general, which is what the scholastics were engaged in. Once you decide you _know_ certain things, then you can end up with all kinds of frankly nutty beliefs based on those priors, following a rock solid chain of rational logic all along, as long as your priors are _wrong_. Scholastics ended up having debates about the nature of the universal intellect or angels or whatever, and rationalists today argue about super human AI. That's really the problem with rationalist discourse in general. A lot of them start with what they want to argue, and then use whatever assumptions they need to start building a chain of rationalist logic to support that outcome.
Clearly a lot of "effective altruists" for example, want to argue that the most altruistic thing they could possibly be doing is to earn as much money as they possibly can and horde as much wealth as they possibly can, so they'll come up with a tower of logic based on far-fetched ideas like making humans an interplanetary species or hyperintelligent AIs, or life extension or whatever so they can come up with absurd arguments like: If we don't end up an interplanetary species, billions and billions billions of people will never be born so that's obviously the most important thing anybody could ever be working on, so who cares about that kid starving in Africa right now. He's not going to be a rocket scientist, what good is he?
One thing most philosophers learned at some point is that you need to temper rationalism with a lot of humility because every chain of logic has all kinds of places where it could be wrong, and any of those being wrong is catastrophic to the outcome of your logic.