The general system of the sciences and the arts is a kind of labyrinth, a

twisting road, which the mind enters without really knowing the route it

ought to take.

Jean le Rond d’Alembert, Encyclopédie (Paris, 1751)

The external conditions which are set for [the scientist] by the fact of

experience do not permit him to let himself be too much restricted in the

construction of his conceptual world by the adherence to an epistemo-

logical system. He, therefore, must appear to the systematic

epistemologist as a type of unscrupulous opportunist.