 Timothy Williamson (2000, pp. 213–7) rejects the connection between a belief having probability 1 and its being absolutely certain. (On his view, one’s evidence is identical with what one knows, so what one knows will be evidence for itself. In a trivial sense, then, everything one knows will have probability 1.) He argues that the connection can be broken by denying that beliefs that have probability 1 at a particular time will always thereafter remain at that probability. Further evidence may be acquired that destroys the knowledge in question; when that happens, it is no longer evidence, let alone evidence for itself. Williamson finds this result congenial because, he says, “it is hard to see how any empirical proposition could have the intertemporal and intersubjective certainty which the conditionalization account demands of evidence” (p. 215). In breaking the connection between certainty and probability 1, then, it is important to keep in mind that Williamson has done so only for absolute certainty (or certainty over time), but not for certainty at a time. See  section 3 below  for more on the distinction between these two dimensions of certainty.