Quotations from Chapter 4 of Edward Gibbon's History of the Decline and Fall of the Roman Empire ("The Cruelty, Follies, and Murder of Commodus — Election of Pertinax — His Attempts to reform the State — His Assassination by the Praetorian Guards (180 - 193 A.D.)"):
But the power of instruction is seldom of much efficacy, except in those happy dispositions where it is almost superfluous.
Yet the arts of Severus cannot be justified by the most ample privileges of state reason. He promised only to betray; he flattered only to ruin; and however he might occasionally bind himself by oaths and treaties, his conscience, obsequious to his interest, always released him from the inconvenient obligation.
(see also Gibbon _-_Table_of_Contents, Gibbon_-_Thoughts_Upon_Reading, ... and http://www.his.com/~z/gibbon.html for a single-page presentation of Gibbon quotes)
(correlates: Gibbon - Table of Contents, Geons, Black Holes, and Quantum Foam, YoursTruly, ...)