In his “Changes of Aspect” (printed for the first time in my article in PMLA, lviii [March, 1943], 223–244), Swinburne writes: “A writer on whom I have lavished what many judges consider an extravagant exuberance of praise has put on record his verdict that a man who never changes his opinion is like standing water—he breeds reptiles of the mind” (op. cit., p. 230). Since my article appeared I have been able to trace the allusion to Blake's “The Marriage of Heaven and Hell”: “… I found myself … hearing a harper …, and his theme was: ‘The man who never alters his opinion is like standing water, & breeds reptiles of the mind’.” (The Poems and Prophecies of William Blake, Everyman's I ibrary, p. 51.)