What were the causes of this change? Was it due mainly to the evil
influence of the principate or to more subtle and deep-rooted causes?

The principate had been denounced as the _fons et origo mali_.[1] That
its influence was for evil can hardly be denied. But it was rather a
symptom, an outward and visible sign of a deep-engrained decay, which it
accentuated and brought to the surface, but in no way originated. We are
told that the principate 'created around itself the quiet of the
graveyard, since all independence was compelled under threat of death to
hypocritical silence or subterfuge; servility alone was allowed to
speak; the rest submitted to what was inevitable, nay, even endeavoured
to accommodate their minds to it as much as possible.' Even if this
highly coloured statement were true, the influence of such tyrannical
suppression of free thinking and free speaking could only have
_directly_ affected certain forms of literature, such as satire, recent
history,[2] and political oratory, while even in these branches of
literature a wide field was left over which an intending author might
safely range. The _direct_ influence on poetry must have been
exceedingly small. If we review the great poets of the Augustan and
republican periods, we shall find little save certain epigrams of
Catullus that could not safely have been produced in post-Augustan
times. Moreover, when we turn to what is actually known of the attitude
of the early emperors towards literature, the balance does not seriously
incline against them. It may be said without hesitation of the four
emperors succeeding Augustus that they had a genuine taste and some
capacity for literature.

Of two only is it true that their influence was in any way repressive.
The principate of Tiberius is notorious for the silence of literature;
whether the fact is due as much to the character of Tiberius as to the