The doctrine of the Real Presence is necessarily contained in the doctrine of transubstantiation, but the doctrine of transubstantiation is not necessarily contained in the Real Presence. Christ could become really present without transubstantiation taking place, but we know that this is not what happened because of Christ’s own words at the Last Supper. He did not say, “This bread is my body,” but simply, “This is my body.” Those words indicated a complete change of the entire substance of bread into the entire substance of Christ. The word “this” indicated the whole of what Christ held in his hand. His words were so phrased as to indicate that the subject of the sentence, “this,” and the predicate, “my body,” are identical. As soon as the sentence was complete, the substance of the bread was no longer present. Christ’s body was present under the outward appearances of bread. The words of institution at the Last Supper were at the same time the words of transubstantiation. If Christ had wished the bread to be a kind of sacramental receptacle of his body, he would surely have used other words, for example, “This bread is my body” or “This contains my body.”
The revealed doctrine expressed by the term transubstantiation is in no way conditioned by the scholastic system of philosophy. Any philosophy that distinguishes adequately between the appearances of a thing and the thing itself may be harmonized with the doctrine of transubstantiation. Right thinking demands that one makes a distinction between what a thing is and what it has. That is part of ordinary common speaking. we say, for example, that this is iron, but it may be cold, hot, black, red, white, solid, liquid, or vapor. The qualities, actions, and reactions do not exist in themselves; they are in something. We call that something the substance. It makes a thing what it is. When we talk about transubstantiation we are using the word substance in that sense. It is unfair for people who do not want to accept this doctrine to invent their own definition of substance and then to tell us we are wrong.
All that substance sustains, the things which inhere in it, we call by the technical name of accidents. We cannot touch, see, taste, feel, measure, analyze, smell, or otherwise directly experience substance. Only by knowing the accidents do we know it. So we sometimes call the accidents the appearances.
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