Although I have known sorrow and great sadness, as is everybody’s lot, I do not think that I have had an unhappy hour as a philosopher since we returned to England. I have worked hard, and I have often got deep into insoluble difficulties. But I have been most happy in finding new problems, in wrestling with them, and in making some progress. This, or so I feel, is the best life. It seems to me infinitely better than the life of mere contemplation (to say nothing of divine self-contemplation) which Aristotle recommends as the best. It is a completely restless life, but it is highly self-contained—autark in Plato’s sense, although no life, of course, can be fully autark. Neither my wife nor I liked living in London; but ever since we moved to Penn in Buckinghamshire, in 1950, I have been, I suspect, the happiest philosopher I have met.
This is far from irrelevant to my intellectual development since it has helped me immensely in my work. But there is also some feedback here: one of the many great sources of happiness is to get a glimpse, here and there, of a new aspect of the incredible world we live in, and of our incredible role in it.
Before our move to Buckinghamshire my main work was on “natural deduction”. I had started it in New Zealand, where one of the students in my logic class, Peter Munz (now Professor of History at Victoria University), encouraged me much by his understanding and his excellent and independent development of an argument.194 (He cannot remember the incident.) After my return to England I talked about the problems of natural deduction to Paul Bernays, the set theoretician, and once to Bertrand Russell. (Tarski was not interested, which I could well understand, as he had more important ideas on his mind; but Evert Beth took some real interest in it.) It is a very elementary but also strangely beautiful theory—much more beautiful and symmetrical than the logical theories I had known before.
The general interest which inspired these investigations came from Tarski’s paper “On the Concept of Logical Consequence”,195 which I had heard him read at a Congress in Paris in the autumn of 1935. This paper, and especially certain doubts expressed in it,196 led me to two problems: (1) how far is it possible to formulate logic in terms of truth or deducibility, that is, transmission of truth and retransmission of falsity? And (2) how far is it possible to characterize the logical constants of an object language as symbols whose functioning can be fully described in terms of deducibility (truth transmission)? Many other problems sprang from these problems, and from my many attempts to solve them.197 Yet in the end, after several years of effort, I gave up when I discovered a mistake I had made. although the mistake was not serious and although in repairing it I was led to some interesting results. These, however, I have never published.198
With Fritz Waismann I travelled to Holland in 1946, invited to a Congress of the International Society for Significs. This was the beginning of a close connection with Holland which lasted for several years. (Earlier I had been visited in England by the physicist J. Clay, who had read my Logik der Forschung and with whom I shared many views.) It was on this occasion that I first met Brouwer, the founder of the intuitionist interpretation of mathematics, and also Heyting, his foremost disciple, A.D. De Groot, the psychologist and methodologist, and the brothers Justus and Herman Meijer. Justus became very interested in my Open Society, and started almost at once on the first translation of the book, into the Dutch language.199
In 1949 I was made a professor of logic and scientific method in the University of London. Perhaps in acknowledgement of this I often began my lectures on scientific method with an explanation of why this subject is nonexistent—even more so than some other nonexistent subjects. (However, I did not repeat myself much in my lectures: I have never used a set of lecture notes for a second time.)
The people from whom I learned most in those early days in England were Gombrich, Hayek, Medawar, and Robbins—none of them philosophers; there was also Terence Hutchinson, who had written with great understanding about the methods of economics. But what I missed most in those days was to be able to talk at length to a physicist, although I had met Schrödinger again in London, and had a good innings with Arthur March in Alpbach, Tyrol, and another with Wolfgang Pauli in Zurich.