Futhermore, judging by the discussion, many people here do not understand at all what Dijkstra is saying, using informal everyday interpretations for technical terms. When he says things about being "formal", it isn't just a synonym for being "systematic", or thinking harder, he means formal as in:

http://en.wikipedia.org/wiki/Formal_methods

http://en.wikipedia.org/wiki/Formalism_%28mathematics%29