Tripping Oozes in D&D (3e versus 4e versus 5e)

A few days ago, someone asked what was the difference between 4e and 5e in an internet forum.

I tried to explain that I liked 5e over 4e because 4e felt too "dissociated" for my style of play, for the lack of a better term. Although I didn't remember the exact mechanics, I felt like 4e (unlike 5e) was a game you could trip a gelatinous cube to make it fall prone. Probably not very helpful, I know.

Fortunately, another user was kind enough  to unearth the exact quote in both 3.5e's and 4e's FAQs:

3.5e FAQ

Things that don’t need limbs for locomotion can’t be tripped. You can’t trip a snake, a beholder, or a gelatinous cube. You won’t find this in the rules, but then it really doesn’t need to be in there—the rules can leave some things to the DM’s common sense.

4e FAQ

Can a gelatinous cube be knocked prone? In situations like this, DMs are encouraged to change the flavor of what is happening without changing the actual rules governing the situation. For example, the ooze could be so disoriented by the blow that it suffers the same disadvantages as if it had been knocked prone until it spends a move action to stand up effectively shaking off the condition.

(Here is the source he mentioned, BTW)

Those little snippets, for some reason, encapsulate the main philosophical difference between 3e and 4e for me. It is no coincidence that the first snippet encourages the DM to use common sense while the second advises against changing the actual rules. This is NOT to say 4e doesn't use common sense, but to highlight the differences between the two approaches.

Art by Jean-Francois Beaulieu - source

I like to play D&D the first way: when the players face a challenge, they describe their actions, and then we find the appropriate mechanic to portray that, using common sense.

Example:
DM: There is a gelatinous cube in the middle of the room!
Player: I hurl a spear at it!
DM: Roll 1d20+BAB against AC 25!
Player: I hit! 15 damage! 
DM: Your spear hits, but barely hurts the creature....

4e, like some other modern RPGs, does things in a different way: when you face a challenge, you find the appropriate mechanic to deal with it, and then you describe the actions in the fictional world that portray the mechanic being used.

Example:
DM: There is a gelatinous cube in the middle of the room!
Player: I use my "tripping attack" power"!
DM: Roll 1d20+BAB against AC 25!

Player: I hit! The cube is knocked prone!

DM: The gelatinous cube is stunned from your attack, so it suffers effects similar to the prone mechanic until it gets the opportunity to shake it off.

The difference is not so much the use of language or even mentioning the name of the power, but the ORDER in which things happen (mechanics then fiction). In 4e, you often deal with challenges using specific game mechanics. You can use the equivalent of "trip attack" on a beholder because there are mechanics for it; if the fiction doesn't allow the beholder to fall prone, you change the fiction.

Most traditional RPGs tend do the opposite: if the fiction doesn't allow the beholder to fall prone, you don't get to use the mechanics for falling prone in the first place. Fiction forces you to change the mechanic.

Of course, things are not black and white. EVERY RPG might include some "mechanics take precedence over fiction" bits. In every edition of D&D, for example, you can have a situation like "Critical hit! You hit him in the middle of the face with your spear! You cause... uh... 5 HP of damage". Which might mean you shouldn't describe the results of a hit until resolving ALL the mechanics (including damage, inspiration, etc) but I digress...

In any case, there are clearly distinguishable shades of gray. Dungeon World, for example, explicitly advises the players against mentioning mechanics when describing heir actions - ever tried to play 4e without mentioning which power you're using?

Nobody is saying you cannot forbid your 4e players from using their tripping attacks against a gelatinous cube, or allow it in 3e. You're the DM, do what you want, as long as everybody is in the same page. But what these FAQs show is that the games are designed around certain mindsets, which can make them more favorable to one method of play over another.

There is no "better or worse", obviously. This goes without saying but I'll say it anyway. Every edition has its fans and followers, every method can be useful for some people in some situations. There is a good point in saying that fighter and rogues will be frustrated if their powers don't work against a large percentage of the enemies they face (no tripping oozes, no sneak attack on undead, etc).

But what about 5e? Well, you definitely cannot trip oozes in 5e, since they are immune to the "prone" condition. That question is, are you unable to trip them because it wouldn't make much sense, or because the mechanics say you can't? Which one comes first? Can you trip a snake, for example? As usual, I'll say that I think 5e is a middle of the road edition, so opinions will vary.

My own opinion - since I haven't found a similar FAQ entry for 5e -  is that you should err in the side of common sense over mechanics. The whole concept of "natural language" (wether you like it or not) leads to this conclusion - 5e seems to prefer changing the rules to match the fiction than the other way around. But it makes sense that some people will think otherwise ("the snake has no immunity against being prone, so I'll trip it!"), and the fact that 5e uses explicit mechanics instead of common sense in this matter supports that theory.

The best way to avoid such discussions in your table is adopting your own FAQ so people know where you stand. Who knows, maybe one day "I allow tripping oozes in my table" becomes an easy shortcut to explain your favorite play-style!