Q: Can you clarify the reason behind placing the Book of the Gospels on the altar rather than in a stand in front of the ambo at the beginning of Mass. GIRM 173 and 175 do not specify the reason. Thank you.
A: Well, I can make up a reason. As you say, no reason is given, so it’s open to discussion.
But I believe it has partly to do with the custom in the Eastern Rites, which leave a book of the gospels flat on the altar throughout the eucharist. I also believe that the two symbols of book and altar are meant to be in close connection with each other, much as cross and altar are. The cross is upright, of course. The book of the gospels lies flat. Christ is present in the gospel, and Christ will be present on the altar. They are the only two items kissed at mass.
Placing the book upright causes practical concerns. The stand is not the symbol – the book is. And if you don’t use a stand, then an upright book could topple, and that would not be a good symbol at all.