Sacramental union (real presence in the Eucharist)

Philip of Hesse brought the leaders of the two Reformations together at Marburg in October 1529 for a plainly political purpose: a united Protestant front needed a united Protestant theology. The colloquy produced agreement on fourteen of fifteen articles. The fifteenth concerned the Lord's Supper, and it did not move.

Luther wrote the words hoc est corpus meum on the table in chalk and refused to be argued off them. His position rested on two commitments. The first was hermeneutical: the words of institution mean what they say unless Scripture itself indicates otherwise, and he regarded Zwingli's reading of is as signifies as the kind of manoeuvre that could empty any text. The second was christological: since the divine and human natures in Christ are united, the properties of the divine nature communicate to the human, and Christ's body can therefore be present wherever he wills, not confined to one location in heaven.

Zwingli held that a body is by definition in one place, that Christ's body is at the right hand of the Father, and that the sacrament is a memorial and a public pledge of allegiance among believers. He read the sixth chapter of John, where Jesus says the flesh profits nothing, as decisive against a bodily eating.

Neither man conceded. Luther is reported to have told the Swiss that they had a different spirit. The Marburg Articles recorded agreement on almost everything and registered the disagreement on this, and the Reformation entered its second decade permanently divided into Lutheran and Reformed camps, with political and military consequences across the following century.

Textbooks routinely label the Lutheran position consubstantiation, and Lutheran theologians routinely object. The objection is not pedantry.

Consubstantiation names a theory: that two substances, the substance of bread and the substance of Christ's body, coexist in the same object. It is a theory of the same kind as transubstantiation and it uses the same Aristotelian apparatus. Luther's whole complaint against transubstantiation was that the church had made a philosophical explanation into an article of faith and anathematised those who declined it. He was not proposing a rival mechanism; he was declining to propose one.

The Lutheran confessional documents accordingly affirm the fact and refuse the explanation. The Formula of Concord of 1577 states that the body and blood are truly and substantially present and are distributed and received with the bread and wine, and calls the union sacramental, distinguishing it from a natural or local presence. The preposition formula, in, with and under, is a way of asserting presence without specifying a spatial or substantial relation. Luther used the analogy of iron heated in a fire, where both iron and fire are present in the same object without either becoming the other.

Two further Lutheran positions follow. The presence is tied to the use, that is, to the action of consecrating, distributing and receiving, which is why Lutherans have not developed eucharistic adoration outside the service as Catholics have. And the presence does not depend on the faith of the recipient: the unworthy receive the body and blood to their own judgement, a doctrine known as the eating by the unworthy, which distinguishes the Lutheran view sharply from the Reformed account in which the believer alone feeds on Christ by the Spirit.