'Et moi ...si j'avait su comment en revenir, One service mathematics bas rendered the je n'y serais point aile: human race. It bas put common sense: back Jules Verne where it belongs, on the topmost shelf next 10 tile dusty canister labelled 'discarded 1lOII- The series is divergent; thCldorc we may be ICDIC'. able 10 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'!tre of this series.