βραχεῖα τέρψις ἡδονῆς κακῆς → the enjoyment from a cheap pleasure is short, there's brief enjoyment in dishonourable pleasure
firmly: P. and V. βεβαίως, V. ἐμπέδως, P. ἀκινήτως; see immovably.
authoritatively: P. κυρίως.