 Most thirteenth-century logic can also be described as post-Avicennan in the sense that logicians in this period all took their departure from Avicenna rather than from Aristotle. In the fourteenth century another transformation took place and the lengthy summaries found in the earlier traditions became very rare. Instead of writing commentaries on the works of Aristotle, Arabic logicians were content with writing glosses. Their interest also shifted from formal logic (syllogisms) to semantic concerns. 