Here is a text purporting to be Julius Caesar's oration contra Cicero, "On the Punishment of the Catiline Conspirators", as preserved by Sallust. This is the opening passage, in which Caesar raises the problem of detecting the truth when the mind is clouded by passions:
QuoteIt becomes all men, conscript fathers, who deliberate on dubious matters, to be influenced neither by hatred, affection, anger, nor pity. The mind, when such feelings obstruct its view, can not easily see what is right; nor has any human being consulted, at the same moment, his passions and his interest. When the mind is freely exerted, its reasoning is sound; but passion, if it gain possession of it, becomes its tyrant, and reason is powerless.