Analysis of The Third Epigram

On an ATHEIST.
Posthumus boasts he does not Thunder fear,
And for this cause would Innocent appear;
That in his Soul no Terrour he does feel,
At threatn'd Vultures, or Ixion's Wheel,
Which fright the Guilty: But when Fabius told
What Acts 'gainst Murder lately were enrol'd,
'Gainst Incest, Rapine,—straight upon the Tale
His Colour chang'd, and Posthumus grew pale.
His Impious Courage had no other Root,
But that the Villaine, Atheist was to boot.