For Cooper-Rompato, the contribution made by medieval sermons to lay numeracy has been underestimated. “Number makes the abstract graspable and understandable” (48), she remarks, revealing thereby that these sermons invoke the counting and rational numbers rather than the abstract numbers of more advanced mathematics (transcendental, imaginary, hyperbolic, etc.). True, many of such numbers had not yet been invented (or discovered), and true again, medieval numbers habitually stay “close to earth” (Jens Høyrup, “Hesitating Progress: The Slow Development toward Algebraic Symbolism in Abbacus-and Related Manuscripts, c. 1300–c. 1550,” in Philosophical Aspects of Symbolic Reasoning in Early Modern Mathematics, ed. Albrecht Heefer and Maarten Van Dyck [College Publications, King's College, 2010], 3–56 (8)). Yet mathematical exploration did flourish—in the abstruse speculations of the Calculators and the calculation innovations of the trade schools. Number's immediacy and concreteness in these sermons do not tell not the whole story of medieval mathematics; nonetheless they contribute to what she calls a “hybrid numerate practice,” which combines basic arithmetic with mystical interpretation of number. She traces this practice in mostly Middle English and some Latin religious literature: the sermon collections of Robert Rypon and of the author of Warminster, Longleat House MS 4, who wrote Dives and Pauper, also considered; the treatise Jacob's Well; and sundry individual sermons, along with the Book of Margery Kempe.

As explained in Chapter 1, number fundamentally inhabits medieval sermons through elaborate systems of division and subdivision that organize and amplify material. Christian numerology also prefers certain numbers: five (wounds of Christ), six (days of creation), seven (deadly sins), ten (commandments), twelve (apostles), and so on. In Chapter 2, the author of Dives and the Longleat manuscript brings God near at hand with numbers—notwithstanding the odd howler. In the parable of the lost sheep, numerological enthusiasm beguiles him into factoring 99 into 9 and 10 (instead of 11). And in noting that there is only one perfect number in each power of ten, the author is right only up to 10⁴ (10,000)—which presumably is as far as he counted. There are occasional lost opportunities to further our historical insight into the mathematics, such as when Pauper observes how the number ten contains all single digits within it (44–45)—a comment that seems to presuppose place value. Cooper-Rompato contrasts the author's optimistic faith in number with the pessimism of Jacob's Well (Chapter 3), where any attempt to tally one's sins founders, because they are “wythoute noumbre” (78–79), even though God knows their exact sum.

This tension between number's ability to reveal God's operation in the universe and inability to fathom the depths of his love (or our depravity) is revisited in the conclusion, where Cooper-Rompato develops arguments about Margery Kempe made previously by Nicholas Watson (“The Making of The Book of Margery Kempe,” in Voices in Dialogue: Reading Women in the Middle Ages, ed. Linda Olson and Kathryn Kerby-Fulton [University of Notre Dame Press, 2005], 395–434). Kempe's relentless enumeration (of sins, souls, pennies, and prayers, to name a few) ultimately exposes number's failure to encompass eternity. There is a philosophical distinction here, however, that calls for clarification. We can speak of the biggest number we can conceive (n) and even add one to it (n + 1). Framed thus, n can always be cashed in for a specific value. Dwelling on such ever-increasing numbers boggles Margery's imagination and inspires an awe akin to Kant's mathematical sublime. On the other hand, infinity (α), treated as a metaphysical totality, resists definition in language; it can be neither plotted on a graph nor included as a limit. A Latin sermon by Oxford theologian John Felton, discussed in Chapter 3, pertains here. Aiming to show how divinity surpasses Euclidean geometry, Felton notes that, whereas a small surface in traditional geometry always has a lesser area than a large surface, a morsel of the Eucharistic host contains the same quantity of grace as does the entire wafer (85). Here indeed is mystery. It would be several centuries before Georg Cantor showed how the infinite set of real numbers could be more numerous—“larger”—than the infinite set of counting numbers; yet, as Felton meditates upon the plenitude of Christ's consecrated body, which never diminishes though it endure endless division, he entertains the paradox that quantities “wythoute noumbre” can occur in different sizes. The point is not simply that God can count higher than we can, but that theology itself becomes the means of mathematical imagining.

Cooper-Rompato's appendix, which summarizes the main ways in which medieval people counted and calculated (by fingers, tally sticks, counters, and pen), complements Chapter 4, on the Latin sermons of Robert Rypon, who, among other things, promiscuously mixes his numeral systems. Using the Greek system to convert the letters of Jesus's name into numbers, Rypon adds them up, then eliminates the zeros—which exist only as Hindu-Arabic numerals—to produce a numerologically significant value. Throughout the sermons cited, one looks in vain for any formal method of marrying language and number. It seems rather that any arbitrary way to extract spiritual meaning from numbers is the right way. Cooper-Rompato correctly notes that the Hindu-Arabic numerals were not used consistently for a couple of centuries (106), but it could have been emphasized how, under-used as they were in daily practice, they may be invoked willy-nilly for the sake of a moralizing riff. Endless creativity characterizes these sermonists’ abilities to find spiritual meaning in quantity. A seemingly inconspicuous number breaks open to reveal hidden truths: thus, the eighteen people crushed by the collapse of the tower of Siloam decomposes into ten commandments (of the old law) plus eight (of the new) (20). Such subdivisions are limited only by the extent of the imagination, and they implicitly invite the hearer to interpret their own experience in like fashion. In her conclusion, Cooper-Rompato notes how frequently Margery Kempe uses spiritually significant numbers to describe ordinary phenomena, suggesting that in her mind the numerological and empirical have converged. Is the numeric parallel between Christ's stigmata and her husband's five head wounds mere coincidence, or has Margery so internalized holy numbers that she now interprets all mundane experience in their terms? Cooper-Rompato's study reveals the importance of sermons in turning daily chores into acts of devotion and using number to transform the mixed life into an imitation of Christ.