“Despite the fact that I am a college graduate and I try hard to make sure our tax returns are accurate…I know that I do not know whether or not my tax returns are accurate, which is a sad commentary on governance in our nation’s capital,” Rumsfeld’s letter reads.

The letter’s phrasing appears to allude to Rumsfeld’s famous “unknown unknowns” statement in 2002, when he said, in reference to Iraqi weapons programs, that “there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns, the ones we don’t know we don’t know.”