This study deals with the development of the sonnet in William Wordsworth. It explains, first of all, the reasons for Wordsworth's return and continuity to write in the sonnet form. Second, it explains how far Wordsworth's sonnets indicate a change in his outlook on life and in his poetic/critical theory. Moreover, it explains how far this change accords with his development in the direction of traditionalism and conservatism and reveals the existence of a conservative streak which continued to grow in him over the years. Consisting of an introduction, four chapters and a conclusion, this study deals with four collections of sonnets written and published by Wordsworth during the period from 1802 to 1822 and traces in these sonnets the development in both Wordsworth's outlook on life and his poetic/critical theory. Thus, the first chapter deals with Wordsworth's early sonnets, which were composed between 1802 and 1807; the second chapter deals with Wordsworth’s sonnets which were composed between 1808 and 1815; the third chapter is devoted to "The River Duddon" sonnets (1820), and the fourth chapter deals with Wordsworth’s "Ecclesiastical Sonnets" (1822).