There are four essential components to Hugh’s definition of a sacrament:
1. A “physical or material” element, such as the water of baptism, the bread and wine of the Eucharist, or the oil of extreme unction.
2. A “likeness” to the thing which is signified, so that it can represent the thing signified. Thus the eucharistic wine can be argued to have a “likeness” to the blood of Christ, allowing it to represent that blood in a sacramental context.
3. Authorization to signify the thing in question. In other words, there must be a good reason for believing that the sign in question is authorized by Jesus Christ to represent the spiritual reality to which it points.
4. An efficacity, by which the sacrament is capable of conferring the benefits which it signifies to those who partake in it.
This new systematic statement of the nature and function of sacraments, though welcome, was nevertheless still imperfect. On Hugh’s definition, penance could not be a sacrament, as it included no material element. Theory and practice were thus seriously out of line. Peter Lombard resolved the matter by omitting one vital aspect of Hugh’s definition – namely, the reference to a “physical or material element.”