He enters into a real union of flesh and blood with it, and binds it to His being even as the branch is bound to the vine. Therefore, the term is defined literally as the process of change of substance. The Catholic Church, in seeking to understand the true presence of Christ in the Eucharist, a doctrine delivered directly by our Lord and St. Paul, gradually developed an explanation as to the exact nature of this miraculous and mysterious transformation. Contrary to the common misconception, transubstantiation is not dependent upon Aristotelian philosophy, since some notion of the concept goes back to the earliest days of the Church when Aristotle s philosophy was not known. The Church did, however, draw upon prevalent philosophical categories, such as substance and accidents.
Accidental change occurs when non-essential outward properties are transformed in some fashion.
A substantial change, on the other hand, produces something else altogether. An example of this is the metabolism of food, which becomes part of our bodies as a result of chemical and biological processes initiated by digestion. In our everyday experience, a change of substance is always accompanied by a corresponding transition of accidents, or properties. In the Eucharist a supernatural transformation a substantial change occurs without accidental alteration. Thus, the properties of bread and wine continue after consecration, but their essence and substance cease to exist, replaced by the substance of the true and actual Body and Blood of Christ.