If you have a binary view, Good will always lose.

Evil can act Good, but Good cannot act Evil. Evil has that advantage over Good that cannot be matched.

This continuously plays out in our political systems. Good actors cannot fight the deluge of evil of their opponents, who are free to lie cheat and steal.

Good binds its own hands. For good to win, it must act with even greater evil. At which point, it becomes the very thing that it tried to defeat.

> Evil can act Good, but Good cannot act Evil. Evil has that advantage over Good that cannot be matched.

The assumption here is that being Evil is advantageous. It's obviously advantageous to personal gain, but the relevant thing is whether it's advantageous to staying in power, and then the system you want to design is the one where it isn't.

Notice also that it isn't binary. You can make it harder to be Evil and then have less of it even if you never have none.

This is assuming a short game. Defection over cooperation dominates short games, but evil can't trust evil in longer play. And I would hope that the default desire is a long game..

Tangent: I think this illuminates why I enjoy the “evil” route in many RPGs. My evil party doesn’t have to be moustache twirling. They can pick and choose their evil moments. But a good party feels more constrained.

Rarely a great RPG forces my good party to make difficult decisions.