'Et moi. ...- Ii j'avait su CClIIIIIIaIt CD 1'CVCDir, ODe scmcc matbcmatK: s bas I'CIIdcRd !be je D', semis paiDt . humaD mcc. It bas put common sease bact Jules Vcmc 'WIIcR it bdoDp, 011 !be topmost sbdl JlCXt 10 !be dully c: uista' t.bdlcd 'cIiIc: arded DOlI- The series is diverpt; therefore we may be sense'. Eric T. BcII able 10 do sometbiD& with it O. Heavilide Mathematics is a tool for thought. A highly ncceuary tool in a world where both feedback and non- 1inearities 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 l'Iison d'etre of this series.