A-Z of the Mass: Transubstantiation

In its decree on the Eucharist, the Council of Trent says that the change (conversio) of the bread and wine into the Body and Blood of Christ, a change that has always been accepted by the faith of the Church, is 'appropiately and properly called transubstantiation'. This change is brought about by the words of Christ and the action of the Holy Spirit. To the question 'what is it?' of the consecrated bread or the consecrated wine, St John Chrysostom and St Ambrose, for example, who are both quoted in the Catechism of the Catholic Church, will already have replied 'it is the Body of Christ, it is the Blood of Christ'. For John Chrysostom, the words of Christ spoken by the priest 'transform the things offered' and Ambrose says that 'by the blessing, nature itself is changed'.

The term 'transubstantiation' emerged only in the middle ages as Catholic theologians continued to reflect on the mystery of this change. In particular they were thinking about the 'is' in the words of Christ spoken by the priest - this is my body, this is the cup of my blood - and came to believe that the least inadequate way to talk about this, in order to give due weight to the mystery believed in faith, was to talk about the substance of the bread being changed into the substance of the Body of Christ, the substance of the wine being changed into the substance of the Blood of Christ.

Thomas Aquinas uses the term transubstantiation to talk about the change. The mode of Christ's presence under the Eucharistic species is unique and raises the Eucharist above all the other sacraments: for Aquinas that presence is the perfection of the spiritual life and the end to which all the sacraments tend. The term 'substance' serves then to underline the reality of this presence (not that the presence of Christ in other ways in the Eucharist and in the Church is not real): a substantial presence is presence in the fullest sense by which Christ, God and man, makes himself wholly and entirely present (so Pope Paul VI).

According to the Catechism of the Catholic Church §1380 it is highly fitting that Christ should have wanted to remain present to his Church in this unique way. Since Christ was about to take his departure from his own in his visible form, he wanted to give us his sacramental presence; since he was about to offer himself on the cross to save us, he wanted us to have the memorial of the love with which he loved us to the end, even to the giving of his life. In his Eucharistic presence he remains mysteriously in our midst as the one who loved us and gave himself up for us. As the Welsh poet David Jones put it, 'he placed himself in the order of signs'. He remains with us under signs that express and communicate His love, and does so particularly in what Catholics call the sacratissimum, the most holy sacrament.