**TAR**) I discovered

**Williamson**'s recent

**paper**(in

**Analysis**) in which he showed just how problematic is the assumption of regularity: that a

*credence*(or subjective

*probability*, or degree of belief, or of acceptance) of 1 implies absolute (not just everyday) certainty; that, conversely, if your credence in some proposition is 0 then you believe that it is impossible. But surely that assumption is clearly fallacious, like assuming that 0 length of a line

*means*no part of a line, whereas points seem to be possible; so I'm wondering why it's so common: Is it something to do with the meaning of

*subjective*probability?