History of the Peloponnesian War
Thucydides
Thucydides. The history of the Peloponnesian War, Volume 1-2. Dale, Henry, translator. London: Heinemann and Henry G. Bohn, 1851-1852.
"I shall, perhaps, appear to you, as some others have done, to speak what is incredible concerning the reality of the expedition that is coming against us: and I know that those who either make statements, or bring reports, which do not seem to be credible, not only fail to convince, but are also thought to be foolish. Nevertheless I will not, through fear of this, hold my tongue when the state is in danger, since I am myself at any rate persuaded that I speak with more certain knowledge than others.
For the Athenians, much as you are surprised at it, have set out against us with a large force both for sea and land service, nominally, on account of an alliance with the Segestans, and for the purpose of settling the Leontines, but really through desire for Sicily, and most of all, for our city, thinking that if they get this, they will easily get the rest also.