Tullius, in sua rhetorica, ad has quatuor omnes alias reducit quia huiusmodi quatuor virtutes cardinales accipiuntur secundum quatuor formales rationes virtutis de qua loquimur.
Cicero reduces all other virtues to these four (De Invent. Rhet. ii) because these four are reckoned as cardinal virtues in respect of the four formal aspects of virtue about which we now shall speak:
Dicuntur principales, quasi generales ad omnes virtutes: utputa quod omnis virtus quae facit bonum in consideratione rationis, dicatur prudentia; et quod omnis virtus quae facit bonum debiti et recti in operationibus, dicatur iustitia; et omnis virtus quae cohibet passiones et deprimit, dicatur temperantia; et omnis virtus quae facit firmitatem animi contra quascumque passiones, dicatur fortitudo.
They are called the principal formal aspects, since they are general, as it were, in comparison with all the virtues: so that, for instance, any virtue that causes good in reason's act of consideration, may be called prudence; every virtue that causes the good of right and due in operation, be called justice; every virtue that curbs and represses the passions, be called temperance; and every virtue that strengthens the mind against any passions whatever, be called fortitude.