A mathematical theory is not to be considered complete until you have made it so clear that you can explain it to the first man whom you meet on the street. (Hilbert)

just now, Lang has published another book on algebraic numbers which, in my opinion, is still worse than the former one. I see a pig broken into a beautiful garden and rooting up all flowers and trees. (Siegel)

In discussing all of these subjects, the author attempts to avoid the axiomatic-deductive style, with its unmotivated definitions concealing the fundamental ideas and methods; similar to parables, they are explained only to disciples in private. (Arnold)