One can't proceed from the informal to the formal by formal means.
When a professor insists computer science is X but not Y, have compassion for his graduate students.
In man-machine symbiosis, it is man who must adjust: The machines can't.
If your computer speaks English, it was probably made in Japan.
Don't have good ideas if you aren't willing to be responsible for them.
Learning French is trivial: the word for horse is cheval, and everything else follows in the same way.