It seems to me sufficient to take all those emperors who succeeded to the empire from Marcus the philosopher down to Maximinus; they were Marcus and his son Commodus, Pertinax, Julian, Severus and his son Antoninus Caracalla, Macrinus, Heliogabalus, Alexander, and Maximinus.
But Pertinax was created emperor against the wishes of the soldiers, who, being accustomed to live licentiously under Commodus, could not endure the honest life to which Pertinax wished to reduce them; thus, having given cause for hatred, to which hatred there was added contempt for his old age, he was overthrown at the very beginning of his administration.
Turning now to the opposite characters of Commodus, Severus, Antoninus Caracalla, and Maximinus, you will find them all cruel and rapacious-- men who, to satisfy their soldiers, did not hesitate to commit every kind of iniquity against the people; and all, except Severus, came to a bad end; but in Severus there was so much valour that, keeping the soldiers friendly, although the people were oppressed by him, he reigned successfully; for his valour made him so much admired in the sight of the soldiers and people that the latter were kept in a way astonished and awed and the former respectful and satisfied.
But let us come to Commodus, to whom it should have been very easy to hold the empire, for, being the son of Marcus, he had inherited it, and he had only to follow in the footsteps of his father to please his people and soldiers; but, being by nature cruel and brutal, he gave himself up to amusing the soldiers and corrupting them, so that he might indulge his rapacity upon the people; on the other hand, not maintaining his dignity, often descending to the theatre to compete with gladiators, and doing other vile things, little worthy of the imperial majesty, he fell into contempt with the soldiers, and being hated by one party and despised by the other, he was conspired against and was killed.
Because it would have been useless and dangerous for Pertinax and Alexander, being new princes, to imitate Marcus, who was heir to the principality; and likewise it would have been utterly destructive to Caracalla, Commodus, and Maximinus to have imitated Severus, they not having sufficient valour to enable them to tread in his footsteps.
Hence it comes likewise, that princes many times make themselves desires, and set their hearts upon toys; sometimes upon a building; sometimes upon erecting of an order; sometimes upon the advancing of a person; sometimes upon obtaining excellency in some art, or feat of the hand; as Nero for playing on the harp, Domitian for certainty of the hand with the arrow, Commodus
for playing at fence, Caracalla for driving chariots, and the like.