A very broad definition of ‘sources’ must be my excuse for considering so familiar a topic as the origins of Macbeth. In this, the most concentrated of the tragedies, a particularly wide diversity of material was fused into unity. “In the quick forge and working-house of thought”, Shakespeare wrought at white heat. The material to be considered falls into three classes. First, the Scottish and English Chronicles supplied the facts, and one important scene; secondly, various works on witchcraft and demonology, including those of King James, gave some material for the witches’ scenes (but here the interest lies rather in Shakespeare’s innovations than in his borrowings); thirdly, earlier works by Shakespeare himself present in a simpler form some of the ingredients of this play, and an examination of what might be called the internal sources elucidates its inward structure. The repetitions, echoes and restatements which are to be detected in Shakespeare offer more than mere opportunity for pedantic correlation; they are alternative statements, varied embodiments of those deep-seated and permanent impulses which underlie all his work and make it, in spite of its variety, a vast and comprehensive whole—a single structure, though of Gothic design.