fert animus causas tantarum expromere rerum,
inmensumque aperitur opus, quid in arma furentem
inpulerit populum, quid pacem excusserit orbi.
invida fatorum series summisque negatum
stare diu nimioque graves sub pondere lapsus
nec se Roma ferens.
My mind hastens to declare the causes of such great affairs,
and the huge work is opened, what drove the raging
people into arms, what shook peace out of the world.
[It was] the envious succession of fates and [the fact that] to the highest [it is] denied
to stand too long and the heavy falls under too great a weight
and Rome not holding herself up.
fert animus causas: Reminiscent of two famous epic openings: fert animus + feminine accusative plural and infinitive recalls Ovid, Met. 1.1-2, (in nova fert animus mutatas dicere formas/ corpora), though here the feminine accusative is the object of the preposition in rather than of the infintive; and Vergil, Aen. 1.8-11:
Musa, mihi causas memora, quo numine laeso,
quidve dolens, regina deum tot volvere casus
insignem pietate virum, tot adire labores 10
impulerit.
Lucan recalls the causas of Vergil and his following indirect questions, including the verb impulerit in first position. But Lucan no longer asks the Muse to tell him the causes; his own mind (animus) hastens along to display them.
quid…inpulerit; quid…excusserit: Indirect questions with perfect subjunctive.
orbi: The ablative of orbis is normally orbe, but the ending in –i is sometimes found.
invida…ferens: I’ve supplied a form of sum here and (following Braund) taken these as answers to the preceding indirect questions.