Now what?

I'm working in an unfamiliar code-base we're trying to revive. The code is in a language I have some experience with but am, none the less, far from expert in. I'm staring at some code that doesn't make any sense to me. Is that because the person who wrote it knew more than I do or the other way round?

Now, generally you'd assume the former because the original author presumably had a vision of what they wanted to accomplish and I'm still trying to piece together a theory of the crime for scattered hints, but in this cases I'm in the middle of refactoring a fairly inexplicable design decision into something more maintainable, so I know the original codew was fallible.

And, of course, there is nothing like a design document or even a few words on what they thought they were doing. All in all, another day at the office.