“…21 The distinction between progress in depth and progress in breadth has been proposed by Zwart (2001: 2). 23 This condition is important to avoid the meaningless cases caused by the irrelevant addition of S and G. Indeed, it would be easy to build an artificial example of a theory deeper than a given theory X by adding to the latter observational and/or theoretical terms irrelevant for O 12 . On the contrary, though Gs are calculated on the basis of Fs, the latter do not determine which are the former.…”