This seems to have been an inspiration of long anterior date; for Mr. Stephens, the surgical fellow-student and fellow-lodger of Keats, says that in one twilight when they were together the youthful poet produced the line-- "A thing of beauty is a constant joy;" which, failing wholly to satisfy its author's ear, was immediately afterwards improved into its present form. Even before handing over any part of his MS. to the printer, Keats, at the "immortal dinner" which came off in Haydon's painting-room, on the 28th of December 1817, and at which Wordsworth, Lamb, and others, were present, had bespoken a strange and heroic fate for one copy of his book; for he made Mr. Ritchie, who was about to set forth on an African exploration, promise that he would carry the volume "to the great desert of Sahara, and fling it in the midst." "Invention" was the quality which Keats most sought for in his "Endymion," as shown in his letter to Mr. Bailey, already cited. He said--"It ['Endymion'] will be a test of my powers of imagination, and chiefly of my invention--which is a rare thing indeed--by which I must make 4000 lines of one bare circumstance, and fill them with poetry.... A long poem is a test of Invention, which I take to be the polar star of poetry, as Fancy is the sails, and Imagination the rudder.... This same Invention seems indeed of late years to have been forgotten as a poetical excellence." The term "invention" might be used in various senses. Keats seems to have meant the power of producing a great number of minor incidents, illustrative images, and other particulars, all tending to reinforce and fill out the main conception and subject-matter. Keats wrote a preface to "Endymion" on March 19, 1818, which was objected to by Hamilton Reynolds, and by his friends generally. It was certainly off-hand and unconciliating, and some readers would have regarded it as defiant. Its general purport was that the poem was faulty, but the author would not keep it back for revision, which would make the performance a tedium to himself, "I have written to please myself, and in hopes to please others, and for a love of fame." There was a good deal more, jaunty and provocative enough. Keats was not well inclined to suppress this preface. He replied on April 9th to Reynolds in a letter from which some weighty words must be quoted:--