“THE most Holy Eucharist has, indeed, this in common with the rest of the sacraments, that it is a symbol of a sacred thing, and a visible form of an invisible grace; but it has also this peculiar excellence, that whereas the others have the power of sanctifying when they are administered, in the Eucharist there is present before administration the very Author of sanctity Himself” (Council of Trent, sess. xiii. chap. 3). Moreover, the Holy Eucharist is not only a sacrament, but also a sacrifice: it is an offering made to God, as well as a source of grace given to men. In the present chapter we shall speak of it as a sacrament, reserving the doctrine of the sacrifice of the Mass for the next chapter.

The peculiarity of this sacrament in being a permanent sign, and in being the Real Presence of our Lord, calls for special treatment differing from that given to the other sacraments. We shall first give the proofs of the Real Presence from Scripture and Tradition; next we shall treat of Transubstantiation, or the mode of our Lord’s presence; and, finally, we shall speak of the matter and form, the minister, the recipient, and the effects of the sacrament.

See St. Thomas, 3, qq. 73–83; Franzelin, De SS. Eucharistiæ Sacramento et Sacrificio; De Augustinis, De Re Sacramentaria, lib. ii.; Wiseman, Lectures on the Holy Eucharist; Dalgairns, Holy Communion.