Beginning in 1909, he taught painting at the Académie Ranson in Paris, where his students included Tamara de Lempicka. She later gave him credit for teaching her the craft technique of painting, though her art-deco style was quite different from his. He also devoted much of his time to writing about theory. In 1909 he published "Théories", which brought together the articles he had written on art since 1890, describing the course of art from Gauguin to Matisse (whose work he disliked) to Cézanne and Maillol, under the subtitle: "From Symbolism and Gauguin towards a new classical order". The book was widely read, with three more editions published before 1920. It included his 1906 essay "The Sun", in which he described the decline of impressionism: "The common error of us all was to search above all for the light. It would have been better first to search for the Kingdom of God and his justice, that is to say for the expression of our spirit in beauty, and the rest would have arrived naturally." It also included his idea that "Art is the sanctification of the nature, of that nature found in everyone who is content to live."