Summary: "De syllogismis" is the fifth treatise of John Buridan's "Summulae dialecticae", a textbook he wrote for his logic course in the Faculty of Arts at the University of Paris. "De syllogismis" contains material related to Aristotle's "Analytica Priora" and Boethius's "De hypotheticis syllogismis". The textbook discusses inferences involving not only propositions de 'inesse', but also propositions featuring oblique, reduplicative and infinite terms. Buridan displays a keen interest in modal inferences and inferences involving propositional attitudes. Buridan's "De syllogismis" continues along the lines of his nominalist conception of the relations between mind, language and reality.