For the past twelve years one Whig historian after another has attempted to turn back the tide of Jacobite studies, meeting with as much success as King Canute. The purpose of this article is to challenge Clyve Jones's conclusions in this journal (“Jacobitism and the Historian: The Case of William, 1st Earl Cowper,” supra, 23, 4 (Winter 1992): 681-96) that Lord Cowper never became a Jacobite, that Lord Orrery was not a key player in the Atterbury Plot, and that the Duke of Wharton was not a committed Jacobite until the end of the plot. Jones uses a discussion of the evidence of Lord Cowper's involvement with Jacobitism as a means of dismissing the whole subject, using the same arguments as previous Whig critics. “James III” and his advisers were wildly optimistic about the prospects of a Stuart restoration and, therefore, their testimony may largely be disregarded. James, on the contrary, was pessimistic by temperament and may be criticized for over caution rather than rashness. The Stuart papers, Jones argues, are not complete. What historical collection is? Despite the gigantic size of the collection, some papers that were brought to England from Rome have disappeared, notably the letter written from the Tower by Lord Oxford in 1716, expressing the utmost indignation at the harsh treatment meted out to him by George I and the Whig ministers and offering his services to James in the management of Jacobite affairs in England. This letter was found by Sir James Mackintosh when the collection was first deposited at Carlton House, but it has disappeared since. An additional difficulty is that after the discovery of the Atterbury Plot by Walpole and Townshend in 1722, Atterbury, Lord Stafford, and Lord Orrery, leading conspirators, destroyed most of their papers before being arrested. Similarly, Lady Cowper destroyed a large part of her diary and a substantial part of her husband's papers at the time of the Atterbury Plot. The papers destroyed were probably more significant than what remains and this helps to explain why Walpole could find so little evidence about the plot that would stick in a court of law. A good deal of material, nevertheless, has survived, and is it too much to ask that it should be used in the same way as any other historical evidence?