One service mathematics has rendered the "Et moi, "'f si favait su comment en revenir. je n 'y serais point alleC human raoe. It hat put common sense back where it belongs. on the topmost shelf next Jules Verne to the dusty canister labelled 'discarded non* The series is divergent; therefore we may be smse'. Eric T. Bell able to do something with it. O. H eaviside 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'elre of this series.