Q: Sometimes the General Instruction of the Roman Missal seems to require different things in different places. Three examples are the altar cross, purification at the credence table and the Gospel Book in the entrance procession.
GIRM 117, says “on the altar or close to it, there is to be a cross adorned with a figure of Christ crucified”. But GIRM 277 has: “The cross, if situated on the altar or near it, is incensed by the Priest before he incenses the altar; otherwise, he incenses it when he passes in front of it.”
GIRM 279 has: “The sacred vessels are purified by the Priest, the Deacon, or an instituted acolyte after Communion or after Mass, insofar as possible at the credence table.” But GIRM 163 has that the Priest “stands at the altar or at the credence table and purifies the paten or ciborium over the chalice”.
GIRM 119 describes what is prepared in the sacristy before Mass and includes: “When the entrance takes place with a procession, the following are also to be prepared: a Book of the Gospels;”. This was added in the 2010 GIRM, it was not in the 1975 GIRM 82. But other parts of the GIRM indicate the Gospel Book is optional or may be on the altar before Mass begins, for example, GIRM 117: “On the altar itself may be placed a Book of the Gospels distinct from the book of other readings, unless it is carried in the Entrance Procession.”
If in one place there is one approach described, should it be followed? I think so. It means consistency. One can be sure that a liturgical law is not being broken. Perhaps the apparent options are for extraordinary situations like a lack of ministers. In the three examples this means a cross on or near the altar, purifications at the credence table and a Gospel Book in the entrance procession. Do you agree?
Given this preference, a related question arises: why do we not have a Gospel Book for week day Masses?
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A: The GIRM is a complex document that has undergone several revisions. I think you’re simply seeing how difficult it is for an editor to catch everything. I don’t believe the GIRM “seems to require different things in different places.” I think it is trying its best to describe the rubrics, including options.
Regarding the gospel book for weekdays, its absence probably relates to its potential cost. However, it could relate to a pastoral preference to solemnize Sundays more than weekdays.