The disputation, or debate, one of the most important university exercises, "first became really established in the schools as a result of the new method." (Cf. page 35.) This exercise was sometimes carried on in the manner of a modern debate; to "respond" in the schools (i.e., to defend a thesis in public debate), and to "oppose" (i.e., to argue against the respondent), was a common requirement for all degrees. Scholars and masters frequently posted in public places theses to the argument of which they challenged all comers, just as a knight might challenge all comers at a tournament to combat. In such cases the respondent usually indicated the side of the question which he would defend. This practice, in a modified form, still exists in some European universities in the public examinations for the Doctor's degree. In another mode, the disputation was carried on by a single person, who argued both sides of the question and drew the conclusion in favor of one side or the other. This was of course merely the oral use of the method of exposition commonly found in the works of scholastic philosophers and theologians. The lecture of Giraldus Cambrensis described above (page 109) was doubtless of this type. A complete example is to be found in Dante's "Quaestio de Aqua et Terra." The brief of the arguments on both sides of this question is here reproduced with some modifications. It illustrates not only the exercise itself, but also the ponderous complications which the scholastic method received at the hands of Abelard's successors, and the weakness of that method when applied to questions of natural science. The reader will note that the argument no longer proceeds by the simple citation of authorities pro and con; the reasonings of the debater are also introduced. Moreover, the argument is more complex. It involves first the statement of the affirmative position; second, the refutation of the affirmative by observation and by reasoning; third, objections to the refutation by reasoning; fourth, refutation of these objections; fifth, final refutation of the original arguments. _Introduction_: Author's reasons for undertaking the discussion.