Programmer: So we’ll see only record types A, B, and C, right?

Finance: Yes. That’s all.

Programmer: Never D? We have some D here.

Finance: Actually, yes. You need to do $special_thing with D records.

Programmer: Okay, so A, B, C, and D after all. That it.

Finance: That’s all. We promise.

(Weeks later)

Finance: Where are my E records?

It’s distressing to me the degree to which rigorous logical thinking is completely alien to corporate finance people. I am reminded of the wise words of my friend R., who said “Normal people don’t see exceptions to rules as a big deal, so they forget to mention them. This is why programmers drink so much.”