LETTER I． Continuation of the Subject， and of Mistakes in the Knowledge of Truth
LETTER II． First Class of Known Truths． Conviction That Things Exist Externally， Corresponding to the Ideas Represented by the Senses， Objection of the Pyrrhonists Reply
LETTER III． Another Objection of the Pyrrhonists against the Certainty of Truths Perceived by the Senses． Reply； and Precautions for Attaining Assurance of Sensible Truths
LETTER IV． Of Demonstrative， Physical， and Particularly of Moral Certainty
LETTER V． Remarks that the Senses Contribute to the Increase of Knowledge； and Precautions for Acquiring the Certainty of Historical Truths
LETTER VI． Whether the Essence of Bodies be Known by Us
LETTER VII． The True Notion of Extension
LETTER VIII． Divisibility of Extension in Infinitum
LETTER IX． Whether This Divisibility in Infinitum Takes Place in Existing Bodies
LETTER X． Of Monads
LETTER XI． Refiections on Divisibility in Infinitum， and on Monads
LETTER XII． Reply to the Objections of the Monadists to Divisibility in Infinitum
LETTER XIII． Principle of the Sufficient Reason， the Strongest Support of the Monadists
LETTER XIV． Another Argument of the Monadists， Derived from the Principle of the Sufficient Reason． Absurdities Resulting from It
LETTER XV． Reflections on the System of Monads
LETTER XVI． Continuation
LETTER XVII． Conclusion of Reflections on This System
LETTER XVIII． Elucidation Respecting the Nature of Colours
LETTER XIX． Reflections on the Analogy between Colours and Sounds
LETTER XX． Continuation
LETTER XXI． How Opaque Bodies are Rendered Visible
LETTER XXII． The Wonders of the Human Voice
LETTER XXIII． A Summary of the Principal Phenomena of Electricity
LETTER XXIV． The True Principle of Nature on Which Are Founded All the Phenomeria of Electricity
LETTER XXV． Continuation． Different Nature of Bodies Relatively to Electricity
LETTER XXVI． On the Same Subject
LETTER XXVII． Of Positive and Negative Electricity．Explanation of the Phenomenon of Attraction
LETTER XXVIII． On the Same Subject
LETTER XXIX． On the Electric Atmosphere
LETTER XXX． Communication of Electricity to a Bar of iron， by Means of a Globe of Glass
LETTER XXXL Electrization of Men and Animals
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