This work, originally written in the form of a letter (see n. 1) became fairly well known in the early eighteenth century because Barbeyrac translated most of it and appended it to his translation of Pufendorf's De Officio Hominis; he also provided an able defense of Pufendorf, and castigated Leibniz for not writing the definitive book on natural law which he (Leibniz) criticized Pufendorf for not writing. Though the argument in this piece is similar to that found in the Meditation on the Common Concept of Justice, pt. IV, particularly, is more rigorous than anything that Leibniz wrote on natural law, and the references to Descartes are of particular interest. Throughout the Opinion it is evident that Leibniz is really attacking Hobbes, or rather all legal positivists, as much as he is criticizing Pufendorf. (The original Latin text is to be found in vol. IV of Dutens' edition; the Barbeyrac translation is appended to the French version of Pufendorf published at Amsterdam in 1718.)

You have asked me on behalf of a friend, most eminent man, whether in my opinion the book entitled De Officio Hominis et Civis, [written] by a man long renowned for his merit, Samuel Pufendorf, is suitable as a topic of instruction for the young. I have re-examined this work, which I had not consulted for a long time, and I have ascertained that its principles suffer from no small weaknesses.