Christians have argued for centuries over the exact meaning of Jesus’ words: “This is my body”. Here are a few thoughts of my own:
The twelve disciples, being Jews, were familiar with the symbolism of the various ingredients of the Passover meal. For example, the unleavened bread was (=represented) “the bread of affliction” eaten by the Israelites in Egypt. There were four cups of wine to be drunk; the third one, the ‘cup of redemption’, represented the blood of the Passover lamb. This was the cup that Jesus said was ‘the new covenant in My blood.’ The disciples would have understood this as vivid symbolism. It would not have occurred to them that the bread and wine were actually transformed into His body and blood, because He was there with them, in the flesh, at the time.
There is also a slight ambiguity in the Greek. “This is my body,” could refer to the bread; alternatively, “This is my body, given for you,” could refer to the whole process of breaking, sharing and eating of the bread. Similarly, “This cup is the new covenant in my blood,” seems to refer to the sharing and drinking of the wine, rather than just the wine itself. It is not so much the elements themselves that are special, but rather the giving and sharing of them. This interpretation puts a greater emphasis on the communal nature of Communion.
Where did the Roman Catholic doctrine of transubstantiation come from? After centuries of debate over the precise understanding of Jesus’ words, it was first promoted as official Catholic doctrine only in 1215, and was then refined a few decades later by Thomas Aquinas. His reasoning was based on the philosophy of Aristotle, who distinguished between the ‘substance’ and the ‘accidents’ of an object. In Aristotle’s mind, the ‘accidents’ were what could be comprehended by the senses (touch. taste, smell); the ‘substance’ was the internal reality. In trans-substantiation, what changed was the ‘substance’, the internal reality.
The problem is, that we no longer think like Aristotle. For us, in the age of science, the ‘substance’ of a thing is its atoms and molecules, its chemical composition (whether detected by touch, taste, smell, or scientific analysis). So in our minds, the substance of the bread that is consecrated in the Eucharist does not change; it remains bread (in terms of its chemical composition). But its significance (the ‘spiritual reality’, if you like) has changed – and changed enormously. To those who believe in Him, it has become Christ’s body.
An analogy that I find helpful is that of paper money. A banknote is not ‘real’ money, but just a piece of paper – an IOU note from the Bank of England. At the material level, it is just paper and ink; but it has ‘added value’ because of the promise printed on it. If the Bank of England were to fail, it would become completely worthless! Yet for practical purposes, we use it as if it were real money – simply because the promise of payment is so utterly reliable. So when I go to the supermarket, armed with my £10 note, I know with absolute certainty that I will be able to exchange it for £10 worth of goods. Similarly with the bread and wine used in Communion, we have Jesus’ word that they are His body and blood. Therefore, even though they are ‘actually’ bread and wine, they can be confidently and completely identified with what they represent.