ingenium eius maioribus1 extuli laudibus quam tu id vere potuisse fieri putas primum quod ita iudicabam. acute movebatur, genus quoddam sequebatur in quo iudicio lapsus, quo valebat, tamen adsequebatur quod probarat;2 multae erant et reconditae litterae. vis non erat; ad eam igitur adhortabar. in excitando autem et in acuendo plurimum valet si laudes eum quem cohortere. habes de Calvo iudicium et consilium meum; consilium, quod hortandi causa laudavi, iudicium, quod de ingenio eius valde existimavi bene.
T 3 Sen. Contr. 7.4.6–8
Calvus, qui diu cum Cicerone iniquissimam litem de principatu eloquentiae habuit, usque eo violentus actor et concitatus fuit, ut in media eius actione surgeret Vatinius reus et exclamaret: “rogo vos, iudices: num,1 si iste disertus est, ideo me damnari oportet?”  ... solebat praeterea excedere subsellia sua et impetu latus usque in adversariorum partem transcurrere. et carmina quoque eius, quamvis iocosa si<n>t,2 plena sunt ingentis animi....  compositio quoque eius in actionibus ad exemplum Demosthenis viget: nihil in illa placidum, nihil lene est; omnia excitata et fluctuantia.
than you believe could have happened truthfully; this was first and foremost because I was of that opinion. He was inspired by a keen intellect; he followed a certain style [i.e., Atticism] in which, though he failed in judgment, in which he was generally strong, he still achieved what he had approved; his reading was wide and recondite. There was no force; therefore I was urging him toward that. And in trying to rouse a man and spur him on, it is of the greatest effect if you praise him whom you admonish. You have my opinion of Calvus and my strategy: the strategy that I praised in order to exhort, the opinion that I thought very highly of his talent.
T 3 Seneca the Elder, Controversiae
Calvus, who for a long time waged a most unequal contest with Cicero for the supremacy in oratory, was so violent and passionate a pleader that in the middle of a court speech of his the defendant Vatinius [cf. F 14–28] got up and exclaimed: “I ask you, judges: surely, just because that man is eloquent, I should not therefore be convicted?”  ... [F 30] ... Moreover, he used to leave his own benches and, carried by the impulse of the moment, would rush right to his opponents’ side. And his poetry, too, though it is lighthearted, is full of great spirit....  Further, his style in court speeches is vigorous on the model of Demosthenes: there is nothing sedate, nothing gentle about it, everything excited and stormy. [continued by F 32]