Originally, the concepts "dissertation" and "thesis" (plural, "theses") were not interchangeable. When, at ancient universities, the lector had completed his lecture, there would traditionally follow a disputation, during which students could take up certain points and argue them. The position that one took during a disputation was the thesis, while the dissertation was the line of reasoning with which one buttressed it. Olga Weijers: The medieval disputatio. In: Hora est! (On dissertations), p.23-27. Leiden University Library, 2005
