It is a problem in literary criticism to know how to use the growing store of material discovered by historical research. This is only the practical aspect of a larger, theoretical problem: the relation between a written work and the biographical experiences of the writer. It has never been doubted that a poet's experiences, public and private, historical and psychological, reappear, distorted, refined, generalized, reordered, in his poetry. Hence it follows that the reconstruction of the poet's experiences from diaries, letters, accounts of friends, and public records, may illuminate his poetry. But the converse of this proposition is also assumed to be true: if the biographical experience illuminates the poetry, the poetry must also illuminate the biographical experience. The poem, in other words, is an autobiographical document.