διάκονος ἐπιστήμη

From LSJ

Ἕκτορ νῦν σὺ μὲν ὧδε θέεις ἀκίχητα διώκων → Hector, you run in pursuit of something unattainable | Hector, now art thou hasting thus vainly after what thou mayest not attain | Hector, now you are hasting thus vainly after what you may not attain

Source

Dutch (Woordenboekgrieks.nl)

hulpwetenschap Plat. Plt. 290c.