Many of his works were published only posthumously, often under arbitrary titles, as Słowacki never named them himself. He also left notes on works that he never began or never completed. Słowacki is also considered the father of modern Polish drama. Polish literary historian Włodzimierz Szturc divides Słowacki's work into four periods: Wolter's circle (pseudoclassicism), Christian ethic, Towiański's ethic and genesic ethic. Other scholars offer slightly different periodizations; for example dividing his works into a classical period, a Swiss period, a Parisian period and a genesis period. Jarosław Ławski combines Towiański's period with the genesic ones, speaking of a "mystical" period. Overall, Słowacki's early work was influenced by Byron and Shakespeare, and included works that was often historical in nature, like (as in "Maria Stuart" or "Mindowe"), or exotic, Oriental locales (as in "Arab"). His work took on a more patriotic tone following the failed November Insurrection of 1830–1831. His final works are heavy in mystical and philosophical undertones. In the 1840s he developed his own philosophy, or mystical system, with works such as "Król-Duch" and "Genesis z Ducha" being an exposition of his philosophical ideas ("genesic philosophy") according to which the material world is an expression of an ever-improving spirit capable of progression (transmigration) into constantly newer forms. As Ławski notes, his philosophical works can transcend clear boundaries of simple literary genres. Słowacki's works, situated in the period of romanticism in Poland, contain rich and inventive vocabulary, including many neologisms. They use fantasy, mysticism and symbolism and feature themes related to Poland's history, essence of Polishness, and relation to a larger universe. Ławski, enumerating the main characteristics of Słowacki's writings, notes first that he was a "creationist", in the sense of creating new meanings and words (many of his characters bear names he invented himself, such as Kordian). Second, he notes that Słowacki was not only inspired by works of others, from poets and writers to scholars and philosophers, but that his texts were often a masterful, ironic-grotesque polemic with other creators.