Dear Marianne,
You don’t sound so much like a heretic as one who is uniformed. Simply because one cannot measure a physical change does not mean that one has not taken place. This is the whole point of transubstantiation. We are dealing with a miracle here. Using the dynamics of scholastic philosophy, the Church’s theology explains where the miracle lies.
Ordinarily what we are used to encountering is a change in the accidents while the substance of something changes–like molding clay into a new shape. The appearance (the accidents) changes, while the substance (what the clay really is) remains the same.
With the Eucharist the very opposite happens. The appearance of bread and wine (the accidents) is what remains the same. But the substance (what the bread really is and what the wine really is) changes. And there is no physical way of measuring this. We know it by faith alone.
Fr. Vincent Serpa, O.P.
