IF YOU have ever opened your Bible at random in search of a prompt to help you make a decision, you have engaged in the type of exercise which is the subject of the letter from Thomas Aquinas to a friend on the subject of “casting lots”. This may not have been a real letter or a real friend. The medieval author was expected to be too modest to express his views without explaining that he had been asked for his opinion by the urgings of others.

The problem is that human beings cannot know the future, but often badly want to do so in order to judge how to act, perhaps only so as to be “advised” for the best or to be helped to choose among a range of possibilities. This clear and reader-friendly first English translation of Aquinas’s De Sortibus sets out his position on all that with the systematic thoroughness that scholastic argument had achieved by the 13th century.

Aquinas explains at the beginning that the actual “casting of lots” has to be considered with a range of “similar activities”, and that one must ask whether these actually work and, finally, whether Christians ought to use them. His sources are chiefly biblical and patristic, but there is unavoidable overlap with the Aristotelian discussion of conditional futurity, which greatly interested contemporary scholars. The modern reader will see common ground with a search for Donald Rumsfeld’s “unknown unknowns”.

Peter Carey provides a collection of modern essays, with a preponderance of Anglicans among their authors, including Andrew Davison who also provides a foreword. These add very helpfully to the context of the work and the questions that it addresses, bringing it very readably into today’s world.

Carey’s partly autobiographical introductory material explains the context of his own longstanding interest in this work, adding considerably to its innate human interest. There is also an appendix on the life and principal works of Aquinas, a chronology, and a selective bibliography.

So, is a Christian permitted to use lots? Aquinas is clear that there must be no deals with the devil. There must be no attempts to “test” God by some action, or to bargain with him in an attempt to get a desired outcome.

Nevertheless, some natural events may have lessons for the observer. A flock of birds suddenly takes to the sky. There may be a reason for that which it is acceptable to consider before making a hasty exit oneself. It may be allowable to cast lots to settle a disagreement about a distribution of goods or to decide who should gain what many want. But, above all, the Christian should trust the Holy Spirit for guidance about what to do.

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

De Sortibus: A letter to a friend about the casting of lots
Thomas Aquinas
Peter Carey, translator
Cascade Books £12
(978-1-7252-8976-5)
Church Times Bookshop £10.80