The historical part of the book consists of fifty-four chapters (c. 10–63). It begins with the second Sirmian formula, and the opposing formula promulgated at Ancyra in a.d. 358. The Sirmian creed being given in c. 10, Hilary, before proceeding to give the twelve anathemas directed against its teaching by the bishops who assembled at Ancyra, explains the meaning of essentia and substantia. Concerning the former he says, Essentia est res quæ est, vel ex quibus est, et quæ in eo quod maneat subsistit. This essentia is therefore identical with substantia, quia res quæ est necesse est subsistat in sese. The Ancyran anathemas are then appended, with notes and a summary.