Frank Ramsey (1903–1930): A Sister’s Memoir by Margaret Paul, with a foreword by Brian McGuinness and an afterword by Gabriele Taylor Cambridgeshire: Smith-Gordon, 304 pp., £20.00 (paper)

“Well, God has arrived. I met him on the 5:15 train.”

Thus, in the New Year of 1929, was Ludwig Wittgenstein’s return to Cambridge announced by John Maynard Keynes in a letter to his wife, Lydia Lopokova. Wittgenstein had previously been at Cambridge before World War I as a student of Bertrand Russell, but had acquired his godlike status through the publication after the war of his first and only book, Tractatus Logico-Philosophicus, which was very quickly recognized as a work of genius by philosophers in both Cambridge and his home city of Vienna. Wittgenstein himself was initially convinced that it provided definitive solutions to all the problems of philosophy, and accordingly gave up philosophy in favor of schoolteaching. In 1929, however, he returned to Cambridge to think again about philosophical problems, having become convinced that his book did not, in fact, solve them once and for all.

What drew him back to Cambridge was not the prospect of working again with Russell, who by this time (having been stripped of his fellowship at Trinity College, Cambridge, because of his opposition to World War I) was a freelance journalist, a political activist, and only intermittently a philosopher. Rather, it was the opportunity of working with Frank Ramsey, the man who had persuaded him of the flaws in the Tractatus. Most significantly, Ramsey had shown that the account Wittgenstein gives of the nature of logic in the Tractatus could not be entirely correct.

Wittgenstein’s belief that he had solved all the problems of philosophy rested on two other beliefs: (1) that those problems arose out of a “misunderstanding of the logic of our language” and (2) that in the Tractatus he had corrected those misunderstandings. Ramsey pointed out that there was something fundamentally amiss with Wittgenstein’s own view of logic, central to which was the insistence that logic is linguistic. Logical relations, that is, hold not between the things or the facts of the world, but rather between propositions. For instance, from the two propositions “If it is raining, the streets are wet” and “It is raining,” we can logically infer a third proposition, “The streets are wet.” That is to say, if the first two propositions are true, the third is necessarily true. The third follows logically from the other two.

According to Wittgenstein, all logic is like this; if there were no language, there would be no logic. And, if there were no logic, there would be no necessity, since all necessity is logical necessity. There is no such thing as a necessary fact. Thus, what Wittgenstein calls an “atomic proposition,” i.e., one that states a simple fact about the world, cannot be necessarily true or false; it has…