They have lately been emphasised in the ingenious and one-sided exaggerations of that brilliant man of letters, Mr.Taine.The social significance and the positive quality of much of their writing is more easily missed, and this side of their work it has been one of my principal objects, alike in the case of Voltaire, of Rousseau, and of Diderot, to bring into the prominence that it deserves in the history of opinion.
The edition of Diderot's works to which the references are made, is that in twenty volumes by the late Mr.Assezat and Mr.Maurice Tourneux.

The only other serious book on Diderot with which I am acquainted is Rosenkranz's valuable _Diderot's Leben_, published in 1866, and abounding in full and patient knowledge.

Of the numerous criticisms on Diderot by Raumer, Arndt, Hettner, Damiron, Bersot, and above all by Mr.
Carlyle, I need not make more particular mention.
_May, 1878._ NOTE.
Since the following pages were printed, an American correspondent writes to me with reference to the dialogue between Franklin and Raynal, mentioned on page 218, Vol.
II.:--"I have now before me Volume IV.

of the _American Law Journal_, printed at Philadelphia in the year 1813, and at page 458 find in full, 'The Speech of Miss Polly Baker, delivered before a court of judicature in _Connecticut_, where she was prosecuted.'" Raynal, therefore, would have been right if instead of Massachusetts he had said Connecticut; and either Franklin told an untruth, or else Silas Deane.
_September, 1878._ CONTENTS OF VOL.

I.
CHAPTER I.
PRELIMINARY.
The Church in the middle of the century New phase in the revolt The Encyclopaedia, its symbol End of the reaction against the Encyclopaedia Diderot's position in the movement CHAPTER II.
YOUTH.
Birth and birthplace (1713) His family Men of letters in Paris Diderot joins their company His life in Paris: his friendly character Stories of his good-nature His tolerance for social reprobates His literary struggles Marriage (1743) CHAPTER III.
EARLY WRITINGS.
Diderot's mismanagement of his own talents Apart from this, a great talker rather than a great writer A man of the Socratic type Hack-work for the booksellers The Philosophical Thoughts (1746) Shaftesbury's influence Scope of the Philosophical Thoughts On the Sufficiency of Natural Religion (1747) Explanation of the attraction of Natural Religion Police supervision over men of letters Two pictures of the literary hack Seizure of the Sceptic's Walk (1747) Its drift A volume of stories (1748) Diderot's view of the fate and character of women CHAPTER IV.
THE NEW PHILOSOPHY.
Voltaire's account of Cheselden's operation Diderot publishes the Letter on the Blind (1749) Its significance Condillac and Diderot Account of the Letter on the Blind The pith of it, an application of Relativity to the conception of God Saunderson of Cambridge Argument assigned to him Curious anticipation of a famous modern hypothesis Voltaire's criticism Effect of Diderot's philosophic position on the system of the Church Not merely a dispute in metaphysics Illustration of Diderot's practical originality Points of literary interest The Letter on Deaf Mutes (1751) Condillac's Statue Diderot imprisoned at Vincennes (1749) Rousseau's visit to him Breach with Madame de Puisieux Diderot released from captivity CHAPTER V.
THE ENCYCLOPAEDIA.
(1) ITS HISTORY.
Previous examples of the Encyclopaedic idea True parentage of Diderot's Encyclopaedia Origin of the undertaking Co-operation of D'Alembert: his history and character Diderot and D'Alembert on the function of literature Presiding characteristic of the Encyclopaedia Its more eminent contributors The unsought volunteers Voltaire's share in it Its compliance with reigning prejudice Its aim, not literature but life Publication of first and second volumes (1751-52) Affair of De Prades Diderot's vindication of him (1752) Marks rupture between the Philosophers and the Jansenists Royal decree suppressing first two volumes (1752) Failure of the Jesuits to carry on the work Four more volumes published The seventh volume (1757) Arouses violent hostility The storm made fiercer by Helvetius's _L'Esprit_ Proceedings against the Encyclopaedia Their significance They also mark singular reaction within the school of Illumination Retirement of D'Alembert Diderot continues the work alone for seven years His harassing mortifications The Encyclopaedia at Versailles Reproduction and imitations Diderot's payment (2) GENERAL CONTENTS.
Transformation of a speculative into a social attack Circumstances of practical opportuneness Broad features of Encyclopaedic revolution Positive spirit of the Encyclopaedia Why we call it the organ of a political work Articles on Agriculture On the _Gabelle_ and the _Taille_ On Privilege On the _Corveee_ On the Militia On Endowments, Fairs, and Industrial Guilds On Game and the Chase Enthusiasm for the details of industry Meaning of the importance assigned to industry and science Intellectual side of the change Attitude of the Encyclopaedia to religion Diderot's intention under this head How far the scheme fulfilled his intention The Preliminary Discourse Recognition of the value of discussion And of toleration (3) DIDEROT'S CONTRIBUTIONS.
Their immense confusion Constant insinuation of sound doctrines And of practical suggestions Diderot not always above literary trifling No taste for barren erudition On Montaigne and Bayle Occasional bursts of moralising Varying attitude as to theology The practical arts Second-hand sources Inconsistencies Treatment of metaphysics On Spinosa On Leibnitz On Liberty Astonishing self-contradiction Political articles On the mechanism of government Anticipation of Cobdenic ideas Conclusion CHAPTER VI.
SOCIAL LIFE (1759-1770).
Diderot's relations with Madame Voland His letters to her His Regrets on My Old Dressing-gown Domestic discomfort His indomitable industry Life at Grandval Meditations on human existence Interest in the casuistry of human feeling Various sayings A point in rhetoric Holbach's impressions of England Two cases of conscience A story of human wickedness Method and Genius: an Apologue Conversation Annihilation Characteristic of the century Diderot's inexhaustible friendliness The Abbe Monnier Mademoiselle Jodin Landois Rousseau Grimm Diderot's money affairs Succour rendered by Catherine of Russia French booksellers in the eighteenth century Dialogue between Diderot and D'Alembert English opinion on Diderot's circle CHAPTER VII.
THE STAGE.
In what sense Diderot the greatest genius of the century Mark of his theory of the drama Diderot's influence on Lessing His play, _The Natural Son_ (1757) Its quality illustrated His sense of the importance of pantomime The dialogues appended to _The Natural Son_ His second play, _The Father of the Family_ (1758) One radical error of his dramatic doctrine Modest opinion of his own experiments His admiration for Terence Diderot translates Moore's _Gamester_ On Shakespeare The Paradox on the Player Account of Garrick On the truth of the stage His condemnation of the French classic stage The foundations of dramatic art Diderot claims to have created a new kind of drama No Diderotian school Why the Encyclopaedists could not replace the classic drama The great drama of the eighteenth century CHAPTER VIII.
"RAMEAU'S NEPHEW." The mood that inspired this composition History of the text Various accounts of the design of _Rameau's Nephew_ Juvenal's Parasite Lucian Diderot's picture of his original Not without imaginative strokes More than a literary diversion Sarcasms on Palissot The musical controversy DIDEROT..