On Certainty is a philosophical book composed from notes written by Ludwig Wittgenstein over four separate periods in the eighteen months before his death on 29 April 1951. He left his initial notes at the home of Elizabeth Anscombe, who linked them by theme with later passages in Wittgenstein's personal notebooks and, compiled them into a German/English parallel text book published in 1969. The translators were Denis Paul and Anscombe herself. The book's concerns are largely epistemological, a recurrent theme being that there are some things which must be exempt from doubt in order for human practices to be possible, including the activity of raising doubts: "A doubt that doubted everything would not be a doubt". The book takes as its starting point the 'here is one hand' argument made by G. E. Moore and examines the role of knowledge claims in human language, particularly of "certain empirical propositions", what are now called Moorean propositions or Moorean certainties. An important outcome is Wittgenstein's claim that all doubt is embedded in underlying beliefs and therefore the most radical forms of doubt must be rejected since they form a contradiction within the system that expressed them. Wittgenstein also sketched novel refutations of philosophical skepticism in various guises.
Gestation
The genesis of On Certainty was Wittgenstein's "long interest" in two famous papers by G. E. Moore, his 1939 Proof of the External World and earlier Defence of Common Sense. Wittgenstein thought the latter was Moore's "best article", but despite that he did not think Moore's 'proof' of external reality decisive. Apparently at the instigation of his close friendNorman Malcolm in mid-1949, Wittgenstein began to draft his response on loose sheets, probably while staying in Vienna in late 1949 and early 1950. He returned to the subject twice more before a fourth and final, highly energetic six week period immediately before his death, when more than half of On Certainty was written. By this time Wittgenstein was using notebooks, recording dates, and marking the topic off separately. Wittgenstein described this final, fertile period in his last letter to Norman Malcolm dated 16 April 1951, thirteen days before his death from the cancer diagnosed in autumn 1949: Nevertheless, on the same day he recorded : "I do philosophy now like an old woman who is always mislaying something and having to look for it again: now her spectacles, now her keys." A week and a half earlier he had written a similar note before OC471: "Here there is still a big gap in my thinking. And I doubt whether it will be filled now."
The text as published
The four parts of On Certainty are of fairly unequal length and only the last is systematically dated:
