Science begins with observation, says Bacon, and this saying is an integral part of the Baconian religion. It is still widely accepted, and still repeated ad nauseam in the introductions to even some of the best textbooks in the field of the physical and biological sciences.
I propose to replace this Baconian formula by another one.
Science, we may tentatively say, begins with theories, with prejudices, superstitions, and myths. Or rather, it begins when a myth is challenged and breaks down – that is, when some of our expectations are disappointed. But this means that science begins with problems, practical problems or theoretical problems.