Robert Forbes, together with Bishop Falconer, was the author the Scottish Communion Office of 1764.  Forbes’ eucharistic theology is found in a work entitled A Catechism Dealing Chiefly with the Holy Eucharist, which was published in 1737-1738.  In this catechism the following questions and answers help to establish Forbes’ eucharistic doctrine:

“Q.  What is the end and design of its institution?

A.To keep up a constant and lively remembrance in our minds of the sacrifice of the death of Christ, and of the benefits which we receive thereby, which can only be done by frequent communicating.

Q.What does the breaking of the bread represent?

A.The breaking or the piercing of the body of Christ.

Q.What does the pouring out of the wine represent?

A.The shedding of the most precious blood of Christ.

Q.Is this Sacrament only a bare remembrance or memorial of Christ’s death and sufferings?

A.No, it is more than that; for by receiving it we solemnly renew our baptismal vow; and, if we partake worthily, we therein have the pardon of our former sins sealed unto us, and we receive new supplies of the grace of God to repair those breaches the enemies of our salvation have made, and to assist us to perform our duty for the time to come.

Q.Are not Christians to believe that the consecrated bread in the Holy Eucharist to be the body of Christ, and the consecrated wine to be the blood of Christ?

A.Yes certainly they are; because our Saviour Himself in His institution of this most holy Sacrament has expressly declared the bread to be His body and the wine to be His blood.

Q.In what sense are we to believe this mysterious doctrine?

A.Though we cannot believe that the bread and wine are the very natural and substantial body and blood of Christ that were upon the cross, yet we are to believe them to be so in a spiritual manner, that is to say, that the consecrated bread and wine are the body and blood of Christ in power, virtue and effect.

Q.By what power is this wonderful change made upon these weak elements of bread and wine?

A.‘Tis certain (as I have already said) from the words of institution that Christ did make the elements to be his body and blood; for He expressly tells us they are so; but no power inferior to His own could make them so.  As therefore the Holy Ghost is His divine Substitute upon earth, by which He is present with His Church unto the end of the world, so whatever operations He now performs in His Church are wrought by that divine Spirit.  Therefore, that the bread and wine may become His body and blood, though not in substance, yet in power, virtue and effect, it is necessary that this Holy Spirit should bless and sanctify them, and work in them and with them. … The bread and wine are the body and blood, not in themselves considered, nor merely by their resembling or representing the sacred body and blood of the adorable Jesus, but by the invisible power and operation of the Holy Ghost, by which the sacramental bread and wine, in the act of consecration, are made as powerful and as effectual for the ends of religion as the natural body and blood themselves could be, if they were present before our eyes. … Even so, in the Holy Eucharist the Consecrated Bread and Wine are called by Christians, and believed to be, the Body and Blood of Christ, according to his own positive declaration, because attended with the same power, virtue and effect for the ends of religion, that his natural Body and Blood could be were they existing with us.” (Forbes, A Catechism Dealing Chiefly with the Holy Eucharist, sections above cited from Stone, 1909: II, 619-620 and Grisbrooke, 1958: 158-159).

Forbes’ work shows that he was presenting a moderate realist doctrine in relation to eucharistic sacrifice and presence.  His answers show that he believed the Eucharist to present a ‘constant’ and ‘lively’ remembrance.  Such a notion is more dynamic than mere remembrance or bringing to mind, and in fact one of Forbes’ answers denies that the Eucharist is a mere remembrance.  The Eucharist is the source of the benefits of Christ’s death, the pardon of sins and the supply of grace.  Clearly he sees the Eucharist as an efficacious means of making available the benefits of Christ’s death in the present.  The effects of Christ’s sacrifice are therefore available in the present in the Eucharist as memorial remembrance or anamnesis.  This is realism to a moderate degree.

In discussing the eucharistic presence Forbes denies any immoderate realism, stating that the natural and substantial body and blood of Christ are not present in the Eucharist, and that instead the body and blood of Christ are present in power, virtue and effect.  It is the Holy Spirit that brings about this presence and indeed Forbes refers to the Holy Spirit as Christ’s divine substitute upon earth.  This implies that the nature of the presence of Christ on earth in the Eucharist is a spiritual presence and that the power, virtue and effect of the body and blood of Christ in the Eucharist is achieved through the power of the Holy Spirit.  The presence of Christ is real in the Eucharist as a spiritual presence.  This does not mean that the bread and wine are just a resemblance or representation of Christ’s body and blood, but that in the power of the Holy Spirit (that is spiritually) they are the body and blood of Christ. 

Forbes’ theology of the Eucharist is based on moderate realism.  He denies any sense of an immoderate presence and sacrifice in the Eucharist, but at the same time affirms a realist link between the sign and the signified.