"Ipso facto" (Latin)
by that very fact -- Webster's New World College Dictionary
noun -- by the fact itself; by the very nature of the deed: "to be condemned ipso facto." -- Dictionary.com
Interestingly, Webster's doesn't say what part of speech it is, but Dictionary.com does. It calls it a noun, but uses it in an example in which it seems to be more of an adverb -- reinforcing my theory that all this language stuff is either 1. the blind claiming they can see as they lead the blind, or 2. a conspiracy to make us all feel stupid.
Indeed, when I turn to a third source, The American Heritage Dictionary of the English Language, Fourth Edition, I see it dubbed an adverb, reinforcing my other theory: I'm good.