Quarrel between Rome and Avignon.—Philip of France and Boniface VIII.—Power claimed by his Bull Unam Sanctam.—Promise of Clement V. to Condemn Boniface VIII.—John XXII. and Nicholas V.—Benedict XII. Corruption of the Fourteenth Century.—Three Councils called by Gregory XII., Benedict XIII., and the Cardinals.—Council of Pisa.—It condemns both Popes, and deposes Them.—Alexander V. elected.—He confirms all the Decrees of the Council.— Three Popes.—Balthasar Costa becomes Pope, as John XXIII.—Council of Constance.—Tries and Condemns Gregory XII., Benedict XIII., and John XXIII.—The Latter found Guilty of Enormous and Scandalous Crimes.— He is deposed, and the Doctrine of the Pope’s Infallibility condemned.—Difficulty in maintaining the Succession of the Popes.—May be two Infallible Popes at same Time.—Corruption in the Council.—John Huss and Jerome.—Their Trial and Death.—Effect in Bohemia.—Martin V.—His Policy.—Violation of his Promise to Alphonso.—His Bull against the King of Arragon.—His Letter to his Legate. Becomes sole Pope.—His Letter to the King of Poland for exterminating the Hussites.—His Death.—Effects of his Reign.