It is strange that contemporary criticism of the Hamlet of Romantic psychology has failed to reckon with an important document of Elizabethan psychology. Professor Stoll has invoked Burton and Professor Schücking, Sir Thomas Overbury; but both the Anatomy and Characters are Jacobean, first published in 1621 and 1614, respectively. There was, however, a book of Elizabethan psychology accessible from 1586, written in English, avowedly to win the general reader, and popular enough for two editions in 1586 and a third in 1613. That Shakespeare used Dr. Timothy Bright's A treatise of melancholie was suggested in 1894 by Richard Loening in support of his theory of Hamlet's physiological melancholy; and in 1899, apparently from independent observation, by Dowden in his edition of Hamlet (p. 77). This suggestion, however, seems to have fallen flat. The title of Bright's Treatise—but not the contents—was known to Stoll, to Schücking, and to Dr. G. A. Bieber, though it is not mentioned by J. M. Robertson, and no reference is made to it in the later studies by Stoll and Schücking. To suggest anew that the Treatise influenced Shakespeare and more particularly Hamlet, is the object of this paper.