 In what follows, I shall consider the most important aspects of Wyclif’s theory of supposition, trying to set it in relation to the medieval tradition of treatises on signification and supposition and particularly to its main source, the theory expounded by Walter Burley in his De puritate artis logicae tractatus longior (composed between 1325 and 1328), which contains an original and intelligent defence of the old view of signification and simple supposition against Ockham’s attacks.