In chess, there’s a niche rule with an untranslated name that amusingly befits its esotericism: en passant. Many casual chess playes are unaware of it. It seems to exist as an afterthought, scribbled in to prevent a pawn from escaping an oncoming enemy pawn by leaping two spaces. It is itself a consequence of another weird rule: pawns in their starting position can move forward two spaces in one move. Why? To speed up the game and relieve some pawn-pushing tedium, I’m guessing.

Chess rules are clean and simple other than the two exceptions above and a third: castling. Under the right conditions, the king can move sideways two spaces, double his usual quota, towards one of his rooks and, inexplicably, in the same move, the rook can leap over the king and nestle beside it. Huh? This move seems normal because of its ubiquity. Casual players usually know it. And yet they are more baffled by en passant, which, compared to castling, is only a small deviation from the core rules.

Once we know the rules of a game, we accept and quit questioning them. We are naturally incentivized to do so, since, the better we internalize the rules, the more easily we can abide by them and get to the business of playing the game. But games are full of weird rules. In basketball, there’s a limit of how long the attacking team can have posession in the other team’s end. Oh, okay. Players on the attacking team in hockey can’t cross into other team’s third of the rink unless the puck is already there. If you say so. In soccer, an attacker must not go beyond the second-to-last player on the defensive team if they want to be passed the ball. Unless they are in their own half, then it’s okay. Sorry?

Weird rules are less weird though when you realize they’re added purposefully to facilitate certain behaviors and prevent others. This applies to laws and regulations, too. They are not corollaries of moral truth, but ways of incentivizing behavior in favor of particular goals. In happy cases, the goals are fairness and fun. But rule-makers are only trying to please the crowd when they themselves are incentivized to do so, by ticket sales, by votes, by social pressure. So next time you encounter a weird rule and you’re curious about its existence, ask yourself: who made this and what are they trying to make me do? And next time you write a rule, ask yourself: what new exploitative behavior will I be incentivizing?