OSR Analysis #12: Gamemastering as Probability Creation

So, I picked up Gygax magazine a few days ago and have been reading through it.  It has been a fun experience, probably a little heavy on the nostalgia department, but then most of the OSR strikes me as having a large component of nostalgia (nothing wrong with that).

The magazine itself certainly brings up fond memories of the heyday of Dragon magazine, when I was introduced to the hobby.

Anyway, I ran across a comment in an article by Lenard Lakofka.  "The DM has the final ability to rule and conduct the game.  If something a player wants to do is outlandish, give it a 3-8% chance of success, but if it's well thought out and doable make it 75-90%.  In those cases, where it is not a sure call in the DM's mind..."  Standard OSR boilerplate "Rulings not Rules" stuff, right?

But it got me thinking.  It strikes me as maybe the dividing line between old school and new school.  In old school, there are a ton of systems - all of which are completely optional (save for usually combat, which holds a hallowed place).  However, the one ur-mechanic which drives old school play is the ability of the GM to create a probability for any situation.  Indeed, that seems to me to be the defining characteristic.

But, what is going on here?  It's the GM's job to judge the worth of an idea, and assign a probability to it?  More than that, such probabilities seem to be neither 0% or 100% as a matter of course.  Is a really, really, really good idea worth 99%?  And a really, really bad one worth 1%?

Now look at a game like Dungeon World.  In that game, all the probabilities are largely fixed - good and bad ideas are going to make it into the mix.  They tend not to be tuned by probabilities, but rather by table consensus and other social factors.  Fiasco also dispenses with such probability assignment, favoring table consensus as well (although it is such a different model of design that there aren't many parallels).

Another new school game, FATE, is on the surface closer to that old school "let the GM judge the probabilities" method.  After all, the GM has a strong stance, and there are skills, with various difficulties assigned for success.  However, the escape hatch comes in the "Create an Advantage" action, which allows a player to put aspects into play.  With enough aspects that may be invoked for free - many actions become not just possible, but true.  In essence, a player is adding to the narration in exchange for success - also a marked difference from that old school philosophy of GM as probability creation engine.

Of course, the difference between old school and new school (to the extent that those nebulous terms even have a center) is much more complex than that, but that quote did strike me as a glaring exemplar of the old school mindset.