Anecdote has it that a professor at my alma mater was presenting a proof to students, stating that X was obvious, before halting and wondering aloud: "Is this r

Anecdote has it that a professor at my alma mater was presenting a proof to students, stating that X was obvious, before halting and wondering aloud: "Is this really obvious?" He examined the blackboard and started pacing for a good 15 minutes mumbling and thinking, before exclaiming with a triumphant expression on his face: "Indeed it IS obvious!" That said, obviously no proof can function without assuming some mathematical background knowledge. This is a paper from a research journal, not a textbook and the readership of the journal where it was published would presumably find this clear.