In one region of our lives, we have no problem in understanding how a thing can change its substance while apparently remaining itself. The process is known as metaphor. ‘Fire’ can mean anger or amorousness rather than literal flame, but the word ‘fire’ remains unaltered in this exchange, rather as the bread and wine of the eucharist still look and behave like bread and wine. Since the meaning of a word is its being, we can say that the being or ‘substance’ of the word has changed with this metaphorical transaction. Flame has transubstantiated into fury.

Moreover, ‘fire’ can act as a metaphor of passion only because there are real resemblances between the two. The relation between the two signs is not iconic (they don’t look much like each other), but it is not arbitrary either. Maybe Seamus Heaney could get ‘carburetter’ to mean erotic passion, but for most of us ‘fire’ is a less laborious way of doing it. In a similar way, the bread and wine of the eucharist, as signs of our human solidarity which need to be destroyed (consumed) if they are to yield life, have natural affinities with the body of Christ. As Herbert McCabe once remarked, you couldn’t consecrate Coke and burgers because they aren’t food and drink.

The notion of metaphor will only get us so far in understanding the eucharist, since a change of being which leaves a thing apparently intact is more mysterious than a change of meaning which does so. But a semiotics of the eucharist can be pressed further.