Quoted from the author's "Preface."
"ThE present work is intended as a sequel and supplement to my History of Greece. It describes a portion of Hellenic philosophy: it dwells upon eminent individuals, enquiring,
theorising, reasoning, confuting, &c, as contrasted with those collective political and social manifestations which form the matter of history, and which the modern writer gathers from
Herodotus, Thucydides, and Xenophon."
"Both Sokrates and Plato, indeed, are interesting characters in history as well as in philosophy. Under the former aspect, they were described by me in my former work as copiously as its general purpose would allow. But it is impossible to do justice to either of them — above all, to Plato, with his extreme variety and abundance — except in a book of which philosophy is the principal subject, and history only the accessory."
"The names of Plato and Aristotle tower above all others in Grecian philosophy. Many compositions from both have been preserved, though only a small proportion of the total number left by Aristotle. Such preservation must be accounted highly fortunate, when we read in Diogenes Laertius and others, the long list of works on various topics of philosophy, now irrecoverably lost, and known by little except their titles. Respecting a few of them, indeed, we obtain some partial indications from fragmentary extracts and comments of later critics. But none of these once celebrated philosophers, except Plato and Aristotle, can be fairly appreciated upon evidence furnished by themselves. The Platonic dialogues, besides the extraordinary genius which they display as compositions, bear thus an increased price
(like the Sibylline books) as the scanty remnants of a lost philosophical literature, once immense and diversified."
And the "Preface" continues for ten more pages.