The Roman Catholic doctrine of the Lord's Supper. Formally defined at the Fourth Lateran Council (1215, under Pope Innocent III) and dogmatically reaffirmed at the Council of Trent (Session XIII, 1551). The doctrine teaches that at the moment of consecration in the Mass the substance of the bread and wine is wholly converted into the substance of Christ's body and blood (Christ's true body and blood, soul and divinity, are then locally and bodily present on the altar), while the accidents (appearance, taste, smell, weight, etc.) of bread and wine remain unchanged. The doctrine rests on substantial Aristotelian philosophical categories (substance and accidents as distinct metaphysical components of physical reality) and on the literal interpretation of Christ's words this is my body (Matthew 26:26; Mark 14:22; Luke 22:19; 1 Corinthians 11:24). The Reformed-confessional rejection of transubstantiation is unambiguous (Westminster Confession XXIX.6: the doctrine which maintains a change of the substance of bread and wine, into the substance of Christ's body and blood, commonly called transubstantiation, by consecration of a priest, or by any other way, is repugnant, not to Scripture alone, but even to common sense, and reason; overthroweth the nature of the sacrament, and hath been, and is, the cause of manifold superstitions; yea, of gross idolatries). Reformed grounds for rejection include: (1) the metaphysical incoherence of substance without accidents in the Aristotelian system; (2) the figurative-speech reading of this is my body consistent with similar Christ-statements (I am the door, I am the vine); (3) Christ's bodily ascension and continuing-bodily presence in heaven (Acts 3:21); (4) the idolatrous consequences of treating the consecrated host as Christ Himself (Eucharistic adoration, Corpus Christi processions, the elevation of the host).