Mycielski mentioned how Mostowski influenced his mathematics and his philosophy: 1. My first teachers of Logic and Foundations were J. Slupecki and J. Los at the University of Wroclaw. But I learned much more more from Mostowski's book "Logika Matematyczna" and Kuratowski & Mostowski "Teoria Mnogosci". At that time the Completeness Theorem of Godel and the Skolem Lowenheim theorem were the great insights that attracted me to LF.Slupecki told me that Mostowski was the most talented logician in Poland, and when I was in Warsaw I always tried to attend his seminar. 2. Now, as an old mathematician and logician I admire the tact and skill of Mostowski. Whenever I had a chance I told him my questions and ideas, and always gotobjective and admirably witty comments. Eventually his "30 Years of Foundational Studies" gave me a stimulating overview of the subject. 3. I remember a conference on algebraic textbooks. The text books of Mostowski and Stark had just appeared. Los was one of the organizers, and he had nothing good to say about their work. And yet it was the deepest and probably the best series of such textbooks in polish. There was astark contrast between the briliant but destructive wit of Los and the constructive wit of Mostowski during that conference. Los kept picking at their textbooks comparing them with thevan der Waerden classic, while Mostowski defended his and Stark's work and challeged Los to write better texts (which never happened). 4. About 1953, the Mostowki family and mine were spending a summer vacation in Ustka. I spend many hours on the beautiful beaches of the Baltic shore talking about mathematics and swimming. The weather was splendid, but every 20 minutes or so a patrol of jet fighters flew at a very low altitude along the shore just above our heads with a terrific noise. I remember Mostowski's remark "we live in an insane azylum". He gave me a little problem, to define a sequenceof natural numbers with a certain growth condition that he needed for a proof in one of his papers. I was able to do it and it made me very happy. I had read earlier a lecture of Mostowski thatgave me a bit of cold feeling since he mentioned materialism in a positive way. I suspected that it was a whiff of Marxism or political correctness. When we talked about it he told me "materialism is a beautiful idea". At that time Poland was reeling under the suffocating propaganda of Soviet Marxism, with vague slogans such as "the principle of unity ofcontradictions", "the law of quantities turning into qualities", etc. Then I realizedthat Mostowski's philosophy was close to Kotarbinski's nominalism and there was nothing vague in it. At that timeI thought that we are free to believe any ontology consistent with verifiable facts. Besides the Soviet rule in Poland was dehumanizingand Catholic personalism was anadmirable opposite of the ideology ofcollectivism and politicization imposed byCommunists. So I did not understand why I should not accept the Catholic ontology, say Thomism, which was presented by the theologians whom I knew. It took me a few years to realize (about 1954) that we are not free to accept arbitrary theories consistent with facts. That we have to obey our innate preference for theories that are the simplest or alternatives of the simplest (at a given level of agreement with facts). And then I understood Mostowski. 5. I studied the proof of the non existence of finite axiomatizability of Peano's Arithmetic invented by Ryll-Nardzewski but written by Mostowski, and Mostowski's own proof of this theorem.But at that time these papers were very difficult for me. In contrast Mostowski's presentation of Godel's constructible setswas admirably clear, and it entailed my admiration for axiomatic set theory. 6. I submitted to Mostowski several papers that he presented to the Bulletin of the Polish Academy of Science. 7. It was a shock when I learned of Mostowski's death.