My Debt to Popper


All that is said below is suspect: it may be an expression of a grudge. Popper broke off relations with me in 1972 and since then he was never ready to acknowledge my existence except in one stormy meeting that we had in 1978 in a Summer School in Alpbach Tyrol, organized by a mutual friend. In our earlier meeting, in 1972, I told him I was going to publish a critical review of his 1972 Objective Knowledge and expressed the wish to discuss that book with him. He said he would if I promise not to publish that review. I said I might do that after the discussion. After a long time our conversation was truncated with no conclusion. He wrote a detailed response to critics of that book, saying he responded to all of them, as if mine does not exist. I find this improper.

I met Popper in my search for a teacher. I was 24 and lost, a graduate in physics (M. Sc., Hebrew University) and an aspiring philosopher in search for a teacher. My interest was in metaphysics, since it was always obvious to me that the sense of proportion is both metaphysical and essential for any significant activity. Yet metaphysics was (and still is) ill-reputed. My aim was to present metaphysics as the tool for interpreting scientific theories. There was a possible teacher in my Alma Mater, the famous mathematician Abraham Halevi Fraenkel, but he was too humble to undertake directing a study in philosophy. My first choice was Einstein, but he was inaccessible. By the time I had the opportunity to visit the United States he was already dead. I went to England in search of a teacher. The only person there recognized as a philosopher of science was Herbert Dingle and I sought his guidance. He was an orthodox empiricist; when we met and he found that my interest is in metaphysics, he kindly erased my registration in his department as an error. Friends of my wife in the London School of Economics advised me to go and see Popper. I refused as I had never heard of him. And then I read his “The Nature of Philosophical Problems and Their Root in Metaphysics” that he wrote after his clash with Wittgenstein, of whom also I had never heard before (and who never interested me as my interest was on the role of metaphysics in scientific research). Before I finished reading that paper, I decided that Popper was to be my teacher. Popper was the first teacher who encouraged my project most significantly, I wrote my dissertation on the function of interpretation in physics under his tutelage. As I told hum many times, I owe him all my achievements, such as they are.

At the time Popper was beginning to free himself from the attitude to metaphysics that he had inherited form Ernst Mach and Werner Heisenberg. Already in his 1935 Logik der Forschung he noted that as scientific theories entail metaphysical ones, that elimination cannot be total. This did not conflict with Mach’s attitude, however, since his aim was to avoid all metaphysical controversy. Popper opposed Heisenberg’s anti-metaphysics as it stood since it was subjectivist, but he offered what he considered an improved version of it. The consistent application of all this to his methodology led to some lovely results. There are all destroyed in Popper’s translation of his magnum opus, his The Logic of Scientific Discovery of 1959 that displays an explicit change of attitude towards metaphysics and surreptitious changes in its detail. All this I noticed much later. What I noticed at the time was his reasoning in his celebrated seminar about metaphysics, where he battled against the then popular, downright silly insistence of Wittgenstein and his many fans that ordinary language precludes metaphysical assertions.

I remember the first Popper lecture in logic I attended. I noticed at once that he was shifting his concern from logic as proof theory to logic as the theory of dialectic. I found it thrilling. I still do. It is still underappreciated.

Popper was the most generous individual I had met. Yet he was also full of suspicion: everyone was a potential thief of his ideas, myself included. The first thing he told me about his lectures was that they were protected by copyright laws. This is true, yet publication was the last thing I could think then. (I did publish his ideas later on.) When I was his assistant, he asked me what my response to his critique of inductivism was. I told him I never was an inductivist, yet I found his solution to the problem of induction just a marvelous breakthrough. He was convinced I was lying, since he knew nothing of Talmudic reasoning, much less my past as a Talmudic student.

He always complained about peers who stole his ideas, and he said repeatedly that his complaint was not priority claims but efforts to respect historical truth. In support of this he stressed that he always was meticulous in acknowledging ideas of others. This is far from the truth. He usually tried to improve upon the ideas that he stole, as if this absolved him from acknowledging debt. He also stole ideas from me, which I did not mind when I was his assistant; I was ashamed for him when he did that later on. My first publication, in 1957, displeased him greatly, as he was convinced it was meant to belittle his originality. He tried to postpone its publication indefinitely. He should have known that he was blessed with great original ideas, so that he could afford to be generous to his less fortunate peers. One idea that he stole from me is utterly insignificant. It is adding the rule of a fortiori to the set of adequacy rules, as Rudolf Carnap called them, in Carnap’s formal system of explication. It proved to me yet again that Carnap was not a serious thinker. When I told him this opinion of mine, it was the first time he was angry with me. And his anger was never frivolous, but at least it was brief and totally ignored. Afterwards he asked me why. I gave him an obvious devastating critique of Carnap and he made song and dance about it and called it a paradox and named it after me. I have later showed that Russell had published that criticism much earlier. The other idea he stole from me was one on which he quarreled with me repeatedly. It was his theory of verisimilitude. He finally endorsed it in a German appendix to his magnum opus (Appendix *XV). He said to me, since he made me a gesture of mentioning me in his Conjectures and Refutations, I should now confess that my criticism is vain. He wrote this to me when I was on my way to visit him and he repeated this when we met, even though my written response condemned his conduct as falsely paying me a compliment.

Despite all the strange weaknesses that Popper exhibited, he was still remarkable, not only as a thinker but also as a person: always understanding and kind and ready to help, never asking for credentials. Nevertheless, his weaknesses were intolerable. Thus, all his students tried to criticize him in order to make names for themselves. This is obvious, since their criticism is so weak that this is the only explanation for their having published it. Sad.

joe_agassi_1Joseph Agassi

Tel Aviv, Israel – Contributor 

Joseph Agassi, FRSC, studied at a rabbinical school, at the Hebrew University of Jerusalem (M. Sc., physics) and at the University of London, where he was assistant to Karl Popper (Ph. D., general science: logic and scientific method). He was a parachute instructor in the Israeli Defense Force. He is professor emeritus at Tel Aviv University and York University, Toronto and Membro Onorario del Corpo Accademico dell’Universita degli Studi “Gabriele d’Annunzio”, Chieti-Pescara, Italia.  

Joe edited about ten books and authored about twenty plus about 600 contributions to the learned press. Among them are Science in Flux, Science and Society, Science and Culture, and Science and Its History; The Siblinghood of Humanity: Introduction to Philosophy, Towards a Rational Philosophical Anthropology; Liberal Nationalism for Israel: Towards an Israeli National Identity;  A Philosopher’s Apprentice – In Karl Popper’s WorkshopThe Hazard Called Education; Ludwig Wittgenstein’s Philosophical Investigations: An Attempt at a Critical Rationalist AppraisalAcademic Agonies and How to Avoid Them.  He co-authored with Yehuda Fried Paranoia: A Study in Diagnosis and Psychiatry as Medicine; with Nathaniel Laor Diagnosis: Philosophical and Medical Perspectives; with Abraham Meidan Philosophy from a Skeptical Perspective; with Ian C. Jarvie A Critical Rationalist Aesthetics; and with David Harel Malevich: the Lost Paintings

Joe can be contacted at


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