Et moi, …, si j'avait Sll comment en revenir. One sennce mathematics has rendered the human race. It has put common sense back je n'y serais point alle.‘ Jules Verne whe , it belongs, on the topmost shelf next to the dusty canister labelled 'discarded non- The series is divergent; therefore we may be smse’. able to do something with it. Eric T. Bell O. Heaviside Mathematics is a tool for thought. A highly necessary tool in a world where both feedback and non- linearities abound. Similarly, all kinds of parts of mathematics serve as tools for other parts and for other sciences. Applying a simple rewriting rule to the quote on the right above one finds such statements as: ‘One service topology has rendered mathematical physics …’; ‘One service logic has rendered com- puter science …’; ‘One service category theory has rendered mathematics …’. All arguably true. And all statements obtainable this way form part of the raison d’!ltre of this series.