 Another anticlosure argument is that there are some sorts of propositions we cannot know unless perhaps we take extraordinary measures, yet such propositions are entailed by mundane claims whose truth we do know. Since this would be impossible if K were correct, K must be false. The same difficulty is sometimes discussed under the heading problem of easy knowledge, since some theorists (Cohen 2002) believe that certain things are difficult to know, in the sense that they cannot be known by deduction from banal knowledge. The argument has different versions depending on which propositions are said to be hard knowledge. According to Dretske (and perhaps Nozick as well), we cannot easily know that limiting propositions or heavyweight propositions are true. These resemble propositions Moore (1959) considered certainly true and that Wittgenstein (1969) declared to be unknowable (but Wittgenstein considered them unknowable on the dubious grounds that they must be true if we are to entertain doubts). Another possibility is that we cannot easily know lottery propositions. A special case of the argument from unknowable propositions starts with the claim that we cannot know the falsity of skeptical hypotheses. We will consider this third view in the next section.