A new chapter in Schiller's life opened with his visit to Weimar in July 1787. Goethe was then in Italy, and the duke of Weimar was absent ; but the poet was kindly received by Herder and Wieland. Not very long afterwards he made the acquaintance at Rudolstadt of the family von Lengefeld, the younger daughter of which subsequently became his wife. Meanwhile the preparation for Don Carlos had interested Schiller in history, and in 1788 he published the first volume of his chief historical work, Geschichte des Abfalls der vereinigten Niederlande von der spanischen Regie rung. It obtained for him, on the recommendation of Goethe, a professorship in the university of Jena, and in Nov. 1789 he delivered his inaugural lecture. Schiller's other historical writings comprise a Sammlung historischer Memoires and Geschichte des dreissigjiihrigen Krieges (1791-93). The latter is written for a wider public than his first history, but the narrative is dramatic and vivid and the portraiture is sympathetic.
Before, however, this work was finished, Schiller had turned from history to philosophy. A year after his marriage he had been stricken down by severe illness, from the effects of which he was never completely to recover ; financial cares followed, which were relieved unexpectedly by the generosity of the hereditary prince of Holstein-Augustenburg, who conferred upon him a pension of 1,00o talers a year for three years. Schiller devoted the leisure of these years to the study of philosophy. In the summer of i 790 he had lectured in Jena on the aesthetics of tragedy, and in the fol lowing year he studied carefully Kant's Kritik der Urteilskraft, which had just appeared and appealed powerfully to Schiller's mind. The influence of these studies is to be seen in several essays, as well as in his correspondence with his friend KOrner. Here Schiller arrives at his definition of beauty, as "Freiheit in der Erscheinung," which marked the beginning of a new stage in the history of German aesthetic theory. Uber Anmut und Wiirde, published in 1793, was a further contribution to the elucidation and widening of Kant's theories; and in the eloquent Briefe fiber die iisthetische Erziehung des Menschen (1795), Schiller proceeded to apply his new standpoint to the problems of social and indi vidual life. These remarkable letters were published in Die Horen, a new journal, founded in 1794, which was the occasion for his gaining the friendship of Goethe. An immediate outcome of the new friendship was Schiller's admirable treatise, Uber naive und sentimentalische Dichtung (1795-96). Here Schiller applied his aesthetic theories to that branch of art which was most peculiarly his own, the art of poetry; it is an attempt to classify literature in accordance with an a priori philosophic theory of "ancient" and "modern," "classic" and "romantic," "naive" and "sentimental"; and it sprang from the need Schiller himself felt of justifying his own "sentimental" and "modern" genius beside the "naïve" and "classic" tranquillity of Goethe's.
For Schiller himself this was the bridge that led back from philosophy to poetry. Under Goethe's stimulus he won fresh laurels in that domain of philosophical lyric which he had opened with Die Kiinstler ; and in Das Ideal und das Leben, Die Macht des Gesanges, Wiirde der Frauen, and Der Spaziergang, he pro duced masterpieces of reflective poetry. These poems appeared in the Musenalmanach, a new publication which Schiller began in 1796. Here were also published the Xenien (1797), a collection of distichs by Goethe and Schiller, in which the two friends avenged themselves on their critics. The Almanach of the following year was even more noteworthy, for it contained a number of Schiller's most popular ballads, Der Ring des Polykrates, Der Handschuh, Ritter Toggenburg, Der Toucher, Die Kraniche des Ibykus and Der Gang nach dem Eisenhammer; Der Kampf mit dem Drachen following in 1799, and Das Lied von der Glocke in 1800. As a ballad poet, Schiller's popularity has been hardly less great than as a dramatist; his bold and simple outlines, his terse dramatic characterization appealed directly to the popular mind. The supreme achievement of the last period of Schiller's life was the series of master dramas which he gave to the world between 1799 and 1804. Just as Don Carlos had led him to the study of Dutch history, so now his occupation with the history of the Thirty Years' War supplied him with the theme of his trilogy of Wallen stein (1798-99). The plan of Wallenstein was of long standing, and it was only towards the end, when Schiller realized the im possibility of saying all he had to say within five acts, that he decided to divide it into three parts, a descriptive prologue, W allen steins Lager, and the two dramas Die Piccolomini and W alien steins Tod. Without entirely breaking with the classic method he had adopted in Don Carlos, Wallenstein shows how much Schiller's art had benefited by his study of Greek tragedy ; the fatalism of his hero is a masterly application of an antique motive to a modern theme. The success of Wallenstein, with which Schiller passed at once into the front rank of European dramatists, was so encouraging that the poet resolved to devote himself with re doubled ardour to dramatic poetry. Towards the end of 1799 he took up his residence permanently in Weimar, not only to be near his friend, but also that he might have the advantage of visiting regularly the theatre of which Goethe was director.