Writing a class without its contract would be similar to producing an engineering component (electrical circuit, VLSI (Very Large Scale Integration) chip, bridge, engine...) without a spec. No professional engineer would even consider the idea.

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

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.

Incorrect documentation is often worse than no documentation.

I think Smalltalk is inappropriate for serious industrial developments. After all, run time is a little late to find out whether you have a landing gear.

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

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.