NOT a good idea, this list," I said, testily, when I was asked to contribute to the selection process. It reminded me of those 100 Great Books university courses in the United States, which never seemed much of a basis for syllabus construction. Unless you are a publisher with an eye on sales figures, why put books in league-tables?

Listing the best Christian books is not a modern idea. Crotchety old Jerome drew up 135 approved Christian authors in the 390s, and called them "Illustrious men". Modestly, he added himself.

Gennadius of Massilia brought the list up to date before he died in 496; but the temptation to update the catalogue continued. Sigebert of Gembloux, 600 years later, extended this list of approved and outstanding authors of Christian books, and put himself at the end in an extra-long section. Authorial vanity still had its place.

The problem seems to be defining what constitutes "best". In Jerome's time, it had still not been finally agreed which books were "scriptural", and ought to be included in the Bible. His "Christian authors" formed a second rank, ahead of the secular classical authors, which he found so hard to put down that he was worried that he was more a "Ciceronianus" than a "Christianus".

MUST books and authors be orthodox, or could they be included if they were dubious but stimulating? Should the criterion be that their popularity endured? Jerome could not check which were favourites on Amazon. He could not look ahead down the centuries and see which would still be "in print" in the 21st century.

Gennadius put in some names about which we should not know at all if he had not listed them; so his guesswork about durability was not very accurate. The works of Jerome's arch-rival, Augustine, bulged in monastic and cathedral medieval libraries - often nearly as frequently as the Bible, and the liturgy. But how many of his works are now on every shelf?

I am not sure that The Consolation of Philosophy, by Boethius, would still be everyone's first resort for consolation, if they found themselves on death row.

So, in what does "bestness" lie? Booker Prize selection, or personal preference? A book for the bedside table, the beach, the condemned cell? Non-fiction, novels, poems, sermons, ebooks and blogs, tracts for their times? The pre-Christian Cicero, who was useful on duty, friendship, and old age? Books written by recluses and the distinctly odd?

A chance sentence in a bad book may still change a life.
 

Dr G. R. Evans is Professor of Medieval Theology and Intellectual History in the University of Cambridge.