Careful as they may be, developers of Eiffel libraries will always run into cases in which, after releasing a library class, they suddenly experience what in French is called esprit de l'escalier or wit of the staircase: a great thought which unfortunately is an afterthought, like a clever reply that would have stunned all the other dinner guests - if only you had thought of it before walking down the stairs after the party is over.

Software entities (classes, modules, functions, etc.) should be open for extension, but closed for modification.

Ask not first what the system does; ask what it does it to!

Eiffel borrows quite openly from several earlier programming languages and I am sure that if we had found a good language construct in C we would have used it as well.

There are only two things wrong with C++: The initial concept and the implementation.

You can either have software quality or you can have pointer arithmetic, but you cannot have both at the same time.

Constants are widely known for the detestable practice of changing their values; we should prepare ourselves against the consequences of such fickleness