  The Roman Catholic doctrine of transsubstantiation led to a discussion of demonstrative phrases. When during the Eucharist the priest takes the bread and utters the words “This is my body,” the substance is said to change from bread into the body of Christ. What then is the referent of the word ‘this’? It cannot be the bread, for that would falsify the sentence, but it cannot be the body of Christ, for the change of substance only occurs when the utterance is complete. In their solutions, theologians discussed a wide range of topics, including the relation between the use and mention of a proposition, the relation of a proposition to the stretch of time during which it is uttered, and the difference between factual and performative utterances, but what concerns us here is their treatment of the word ‘this’. Priscian’s reference to intellectual demonstration was found useful, and the thought that a demonstrative could refer either to something absent or to something spiritual was supplemented by a further kind of intellectual demonstration in which the thing actually pointed to is not numerically identical to the thing signified and to which the predicate applies. “This herb grows in my garden,” said while in someone else’s garden, was the standard example here. Aquinas seized on Priscian’s further claim that demonstratives signify substance without quality, and argued that ‘this’ refers to something indeterminate which is first qualified by the properties of bread and then by the properties of Christ’s body. 