What do we know about Giorgio Diaz de Santillana? Why he is so relevant for history of science? Complex and eclectic scholar in history of science, de Santillana has seen to these days little to no attempts at discussing his view, and those attempts are usually focused just on specific topics. In this talk I aim to analyse his works about historiography of science, from the first books with Federigo Enriques, until the last work written with Hertha von Dechend. I aim to show how in his thought there is a common thread that connects his writings. But social and political interests were steady in de Santillana’s life. I tried to understand institutional commitment and his political and social reflections. I did that work using documents found in the Institute Archive and Special Collections of MIT.  So in this talk I aim to explain what I found there and some of the most interesting projects, for example the creation of institutes for history of science. The first of these projects concerned the creation of a degree course and a research center in history of science at MIT. The other one concerned the creation of an Institute that should had been a synthesis between Science and Humanism, in Venice. In his works he ever underlined the figure of the scientist in society, in particular in his book The Crime of Galileo and in the conference Galileo and Oppenheimer. This reading of society is a mirror of de Santillana's political commitment.