Marbod von Rennes Illustration of Marbod of Rennes and his Latin book of stones

Why a bishop puts herbs and gemstones in the same line

Marbod of Rennes (c. 1035–1123), a poet and bishop from western France, introduces his Latin book of stones with a comparison. Anyone who can identify a plant by its smell or knows what a particular herb is used for already has some idea of what the word “power” might mean. Marbod calls on precisely that experience before he turns his reader’s attention to stones.

Two realms of nature in one line

Great power is given to herbs, the greatest to gems.

– Marbod von Rennes, Liber lapidum, 1799, p. 7.[1]

The poet can take the power of herbs largely for granted in the first half of his line. The second half takes him further than some of his readers may have expected. He needs the Latin word virtus only once. It does duty for both realms, which makes the rise from “great” to “the greatest” all the more audible. The preceding line also helps to explain what it means for this power to be given. Marbod understands it as something God has placed in the stones.

Who should be trusted with the book?

The prologue also considers whom its reader should share the book with. Its knowledge of the hidden powers of stones deserves, in Marbod’s view, readers who have judgement and discretion. He suggests that an effect might be visible even while its cause remains hidden. This opens a question that accompanies the descriptions to follow. A reader with a specimen in hand can inspect its colour and surface. Much else that is said about the same piece must reach that reader through another person’s account. Marbod’s compact line offers a glimpse of the trust on which this medieval way of studying nature rested.