Why doesn’t this just amount to infallibilism, and so a dramatic shrinking of what we can be said truly to know? Because, according to Lewis, the extension of ‘every’ is restricted to a particular conversational domain (ibid., 553–554). Thus, Lewis thinks, certain not-p possibilities will be “properly ignored” in any given situation. As to what determines whether a given possibility is properly ignored, Lewis suggests a number of rules, including the Rule of Attention: “a possibility that is not ignored is ipso facto not properly ignored” (ibid., 559). And this is why the skeptic’s argument is so irresistible, Lewis thinks. For skepticism—indeed, epistemology generally—just is the making salient of certain possibilities of error. For example, to consider whether we know that we are not BIVs, as assessing the first premise of SA requires, is ipso facto not to ignore that possibility. One’s evidence definitely does not eliminate the possibility if it consists in one’s experiences. So we do in fact have lots of knowledge, according to Lewis, but it is “elusive”: “Examine it, and straightway it vanishes” (ibid., 560).