Descriptive vs Prescriptive RPG Structures

Today in talking with Phil Vecchione about trying to use Powered by the Apocalypse thinking in Fate, I said Fate has a descriptive structure. PbtA has a prescriptive structure.[1] They don’t just blanket work together. I know, I tried to meld them for years.

In Fate, when you want to do something, there’s a fuckton of flexible negotiation. We decide which rules are the most appropriate to engage in based on action and intent. The same action on the surface could be an Overcome or Creating an Advantage, most notable when trying to uncover secrets.

Sometimes the opposition is active (someone hiding their intent from you in the moment). Sometimes the opposition already happened (someone hid evidence of their crime). Sometimes the opposition is passive (weather tainted the evidence). And you can combine the latter two pretty simply.

Then the GM decides the difficulty and if there’s an opposed roll or flat target number. You figure out if the most appropriate failure outcome is a block or success at a cost. You figure out if the success outcome is narrative or mechanical. The rules tell you how to describe situations, but not demand you follow a path. Player intent, character action, and GM knowledge/intent all play together in that process.

Powered by the Apocalypse is all about paths sparked by actions. There is no negotiation. You do X, you roll Y, and some defined result happens. The execution of that result is handled by people, but what path you take is defined.

PbtA structures are very attractive. Prescriptive frameworks feel great for solving hard design problems, like discovering information. They are safety nets that allow GMs to not have to make hard decisions. But they’re fragile in a descriptive environment. The GM is arbiter, and in a game like Fate the whole group is meant to participate in that arbitration to at least some degree.

Fate’s descriptive structure is attractive as well. It’s an easier design. Flexibility is easy to write. But you can’t put that in a prescriptive structure without creating distrust in the system. You’re placing a piece of mechanics that are about handing arbitration to the GM in a space where the system is meant to be that arbiter. That creates trust issues in the system itself.

(This gets weird when you talk about rules regarding assault, until you realize the point of assault-based rules is to measure time-to-deagency and to create trust and risk around that.)

When you port one of those partial structures into the other sort of game to solve a momentary design question, you’re opening up the question of: why not do that for everything? If you’re gonna, say, prescribe information gathering in Fate, why not prescribe momentary manipulation? Cornering someone in a bar? Well, everything?

I’m not saying you can’t port partial structures from one to another, but those mechanics need way more field testing and guidance than you think. They more than others need love from people outside of you and your direct circles, because your biases will reinforce your playtesting of those mechanics and they’ll appear to work. And at a certain point, that guidance becomes a weight better served by moving to the core structure than trying to force another one in.

That said, if you’ve seen them work with a bunch of independent testing, I’d love you to point to published games!


[1] My linguist partner is gonna ream me for abusing descriptivism/prescriptivism this way.