K ⊈ E

In a series of very influential works, Tim Williamson has advanced and defended a much discussed theory of evidence containing, among other claims, the thesis that, if one knows P , P is part of one's evidence ( K ⊆ E ). I argue that K ⊆ E is false, and indeed that it is so for a reason that Williamson himself essentially provides in arguing against the thesis that, if one has a justified true belief in P , P is part of one's evidence: together with a very plausible principle governing the acquisition of knowledge by non‐deductive inference based on evidence, K ⊆ E leads, in a sorites‐like fashion, to what would seem a series of unacceptably bootstrapping expansions of one's evidence. I then develop some considerations about the functions of and conditions for evidence which are suggested by the argument against K ⊆ E . I close by discussing the relationship of the argument with anti‐closure arguments of the style exemplified by the preface paradox: I contend that, if closure is assumed, it is extremely plausible to expect that the diagnosis of what goes wrong in the preface‐paradox‐style argument cannot be used to block my own argument.