It never ceases to amaze me the latitude the Church permits in explaining how the reality defined by her dogmas comes about.
For example, it is a dogma that the whole substance of bread is converted into the whole substance of the body of Christ, and that this change is fittingly called transubstantiation.
One of the great questions that divides Scotists from Thomists is- “WHAT does that mean?”
Both agree the bread and wine are substantially changed. But how?
The Thomist will hold to transubstantiation via production- the substance of bread undergoes an interior ontological change via mutation into the ontological body of Christ. The substance of bread BECOMES by a mutation and conversion, the substance of Christs body.
The Scotist will hold that the act of transubstantiation is a substantial change of PRESENCE, not the production of a new substance. You cannot add to or multiply Christs ONE body in heaven, so the transubstantiation is essentially the substance of bread being entirely displaced by the new presence of Christ being called to the altar by the act of the priest.
Now, on first glance, it seems the Thomistic understanding is the correct one. But if we analyze it and ask some serious questions, we have some problems-
If the change of the substance of the bread is an act of mutation of one substance into another, of bread into the body of Christ, is this change INSTANTANEOUS or GRADUAL?
If it is gradual, is there a moment in time where the host is not entirely the body of Christ, but a mingled substance of body and bread? If so, at what point? Is there ever a moment where the priest risks idolatry by adoring the wrong part of the host? If not, then the change in the host from bread to body is instantaneous and a definite line can be drawn between the host in one instant and the body of Christ in the next instant.
But, if the change in the host is instant, stark and entire, in what sense is this a substantial CONVERSION? We perceive a definite before, and a definite after, but not a definite “becoming” via mutation. How then is the effect of the consecration (Christs body) connected with the substance it changed from, ontologically? Where is the “becoming”?
And if there is no strong ontological connection between the substance that exists first (the bread) and the substance that comes after (the body), because there is no sense in which change by ontological mutation can be considered gradual, then we are not REALLY describing an ontological change of substances morphing into other substances, but rather of one entirely new PRESENCE of one substance displacing the other.
Enter blessed John Duns Scotus. The transubstantiation of the eucharist is not a transubstantiation of production, but ADDUCTION, calling forth a presence, not the ontological mutation of substance. In other words the entire substance of THIS bread, gives place to the entire substance of THIS body, a substantial change of presence that situates itself directly in the location of the accidents of bread and wine, which lend the change a focus sufficient to call it a conversion- but not of ontological substance, but substantial presence.