Wittgenstein's On Certainty was first published in 1969, and as all exegetes know, it was his last work,¹ the final seven entries being inserted into the manuscript only two days before he died. Professor von Wright's essay, "Wittgenstein on Certainty," was delivered at a conference in Helsinki in August of 1970, and as he later pointed out "it was at the time of its composition perhaps the fullest presentation of the newly published Über Gewißheit (class="EmphasisTypeItalic ">On Certainty) containing Wittgenstein's latest philosophical writings."² As far as I know, it was also the first study of On Certainty to appear in print.