AbstractThe purpose of this study was to describe the characterization of the major figures in the six novels of Thornton Wilder and to show that two predominant themes, one, moral, the other, religious, are illustrated in the characterization of the major figures. The novels, written during four decades are the following: The Cabala (1926), The Bridge of San Luis Rey (1927), The Woman of Andros (1930), Heaven' s My Destination (1934) , The Ides of March (1948), and The Eighth Day (1967).The research entailed a close examination of the six novels and of the criticism regarding each novel. It also included a careful reading of Thornton Wilderts remarks on the novel and on characterization within that genre.The dissertation was divided into two parts: the description of the characterization in the six novels and the illustration of two themes by means of that characterization. The description of the characterization was limited to that of the major individuals in each novel, because it is through their delineation that the two predominant themes are illustrated. The description of the characterization was then divided into three parts: the patterns of characterization in the six novels; the specific delineation of major figures in the first three novels; and the specific delineation of major characters in the last three novels.In separate chapters the moral theme and the religious theme were traced throughout the six novels. Theme was used as a concept expanded upon within the novels. Each theme was shown with variations in intensity and expansion of expression, the variations running sometimes parallel and sometimes contrapuntally. The expansion of the themes by means of variations and repetitions made them resemble melodic motifs in a symphony.The moral theme, one's search for the way to live, was derived from Pamphilus's question in The Woman of Andros: "How does one live?" The religious theme was based on Caesar's question in The Ides of March: "Is there a Mind in or behind the universe which is watching us?" This theme included not only man's search for a divinity or Supreme Being, but his desire for knowledge for his relation to that Being and of the extent to which such a Being governs man's destiny.The description of the characterization disclosed several patterns in Wilder's delineation of a wide range of characters from varying milieux. Reasons were suggested in the three descriptive chapters for the fact that some of these patterns vary while others remain constant. It was noted that Wilder's characterization in the first three novels illustrates his concept of the function of the novel; that his characterization definitely improves in Heaven's My Destination and The Ides of March, where he moves to indirect delineation through speech and action; and that his characterization shows development in his last novel, The Eighth Day, in its expansion to include delineation of characters not only as complex individuals within a group or community, but also as products of their past and their environments and in relation to parental influences.It was suggested that the illustration of the moral and religious themes through the characterization exemplifies both Wilder's justification of narration on the basis of the ideas it presents and his desire to include moral and religious concepts within his works. The study also showed that the moral theme is the more constant and that the religious theme reveals Wilder's progression from ambivalence to serious consideration to emphatic affirmation.