"Q"

I periodically get a shipment of new Paternoster titles from England. Some of them contain some real jewels. This one is from The Three Gospels, page 91:

I think it may be stated without exaggeration that Q is the most successful fallacy in the history of scholarship. It owes its success to the fact that it has acquired a name – the letter, ‘Q’ – which can be, and has been, reinterpreted every time the current theory encounters a problem. So ‘Q’ has a wide variety of meanings, any one of which can be called upon when required. It has thus the nature of a hydra, each of whose heads has to be cut off before it will die.

This same shipment contained a book titled Eschatology and Pain in St. Gregory the Great. Isn't that an intriguing title?