The biochemist Otto Warburg lectured already at the first Lindau meeting in 1951, but no known transcription of his lecture exists. But from the title we know that it concerned photosynthesis, an example of which is the process in which green plants with the help of light and water take up carbon from the air. Warburg lectured on other aspects of photosynthesis also in 1954 and 1963, while for his last lecture in Lindau (1966) he chose the subject of cancer. During the time span 1951-66, the Lindau meetings in medicine transformed from catering mainly for specialists to catering for a broad audience consisting more and more of young researchers and students. Warburg’s choice of topics raises a general question, which is of interest also today: Should the young people in the audience believe everything that a Nobel Laureate tells them just because he/she has received the Nobel Prize? It is quite clear that Warburg was an exceptionally gifted biochemical experimentalist and that he also made at least one discovery of Nobel stature. But it seems that he used the results of some of his experiments to construct theories that were not accepted by the scientific community. The two areas, in particular, in which Warburg’s theories met resistance, were the ones he lectured on in Lindau: Photosynthesis and Cancer! With regard to photosynthesis, his theory was built on the hypothesis of a maximum quantum yield and turned out not to be applicable. Warburg was known to defend his own ideas vehemently and this may possibly explain why Melvin Calvin, who received the 1961 Nobel Prize in Chemistry for his explanation of the way plants assimilate carbon dioxide, chose not to attend the Lindau meetings until 1974, when Warburg had passed away. As regards the topic of cancer, Warburg’s 1966 lecture gave an explanation of the cause of cancer that today is looked upon not as a cause but rather as an effect. His ideas about cancer also led him to live his life in a rather eccentric way and he eventually became what one could term a food fundamentalist. By acquiring a large area adjoining his house in Berlin, he could grow his own fruits and vegetables and keep his own small animals for food production. He baked his own bread and even, from specially delivered organically “clean” milk, separated out cream and made his own butter. So in answer to the question posed above, my personal recommendation to the young people in the audience is: Always keep an open but critical mind!