Littré started work on his great "Dictionnaire de la langue française" in about 1844, which was not to be completed until thirty years later. He participated in the revolution of July 1848, and in the repression of the extreme Republican Party in June 1849. His essays, contributed during this period to the "National", were collected together and published under the title of "Conservation, revolution et positivisme" in 1852, and show a thorough acceptance of all the doctrines propounded by Comte. However, during the later years of his master's life, he began to perceive that he could not wholly accept all the dogmas or the more mystic ideas of his friend and master. He concealed his differences of opinion, and Comte failed to recognise that his pupil had outgrown him, as he himself had outgrown his master Henri de Saint-Simon.