- "Everything in Mathematics that can be categorized, is trivial" (P. J. Freyd), which should be understood as: "category theory is good ideas rather than complicated techniques". - "I always disliked Analysis" (P. J. Freyd)
Un qualsiasi campo costante. Poi con la norma euclidea per dare un campo $C^(infty)(RR^n)$ basta fissare una base e dare $n$ funzioni scalari classe $C^(infty)$ tipo