I wondered for a while whether the usual meaning of empirical ("knowledge based on experience") is derived from a tenuous conection with the word and concept of Empire, and so could the word actually have been the right one in the context?
I have now looked up the derivation (while enjoying my coffee and eating my ginger biscuits) and discovered that "The English term empirical derives from the Ancient Greek word ἐμπειρία, empeiria, which is cognate with and translates to the Latin experientia, from which are derived the word experience and the related experiment. The term was used by the Empiric school of ancient Greek medical practitioners, who rejected the three doctrines of the Dogmatic school, preferring to rely on the observation of "phenomena"
So now we know! #anotheruselessfactforpedantscorner