M. Tullii Ciceronis De natura deorum libri tres

In the Preface to my former volume I expressed a hope that the remaining volume might be completed for publication before the end of the year 1881. This hope has been disappointed partly owing to the labour of expanding into a separate work the Sketch of Ancient Philosophy, which formed part of the Introduction to the First Book, and partly from the unforeseen difficulties which I have encountered in the endeavour to explain fully the scientific views of the Ancients, as they are reported by Cicero in his Second Book. The consequent increase in the size of the Commentary has made it necessary to devote a whole volume to this Book, and the publication of the third and last Book must still be deferred to another year.