 Burley’s views are especially interesting for historians of logic and metaphysics because of their originality, wide influence, and development. Twice during the course of his academic career, in the first and third decades of the fourteenth century, Burley worked out slightly different versions of the same semantic theory in connection with two different conceptions of reality. The first version (elaborated in De sup., QP, the middle commentaries on Aristotle’s Categories and De interpretatione, and Ean) is somewhat less sophisticated than the second (elaborated in De puritate artis logicae, tractatus longior, the last commentaries on the Physics and Ars Vetus, and theTdU). Whereas in his early works Burley was able to differentiate the intension of an expression (the universal form) from its extension (the individuals instantiating that universal form), in his last commentary on the Ars Vetus he distinguishes between sense (the mental universal existing in the mind as an object of understanding) and reference (significatum) of an expression, which in turn is divided into its intension (the universal) and extension (the individuals).