Addendum to 'Notes on Rhetoric' posted by Richard Seymour

You know perfectly well/Obviously.... This is a perfect argumentative recourse when you wish to make a point about which you are uncertain. You make up for your own uncertainty by imputing a surfeit of certainty to your opponent. Knowing your point is dubious, or impossible to substantiate, repeatedly assert that it is 'obvious'. Variants include, "you know full well that", "as you are perfectly well aware" or "you say that as if you didn't know better". If you are given to fustian language, you could also signal a bit of condescension at the same time by affirming that your point is "elementary". (Cf. Norman Finkelstein on Christopher Hitchens: "It's almost an inside joke as he signals each ridiculous point with the assertion that it's 'obvious.'")