In 1978, being at a loose end, I looked at some books in the British Museum (as it was) that had belonged to the Elizabethan magus John Dee. In the margin of one, in his neat italic hand, he had added up the numeric values of the letters of his name. They came to 666. I found this a bit chilling. Dee was practising the Hebrew cabbalistic art of gematria. The system can seem arbitrary, though not often so dark. And now the productive scholar Francis Young has found that interest in a sort of Christian Cabbala was taken by a less dubious figure, Sir Thomas Tresham (1543-1605). I wrote about Tresham here in 2013 when the updated Northamptonshire volume came out in the admirable Pevsner series of architectural guides. Tersham’s remarkable Triangular Lodge at Rushton was called in that volume: “No more nor less than a profession of faith in stone.” That is right. It was built as a kind of psalm to God the Holy Trinity, with threes everywhere. Tresham was not familiar with Christian esoteric ideas taken from the Jewish Kabbalah (as it is spelt by convention) when he built the Lodge, Dr Young says. But he was fascinated with mathematical analyses of the cosmos as presented by such figures as the 13th-century Ramon Llull (whom Leibniz later respected). Tresham was imprisoned for most of 1581-97 because of his Catholic faith. (For not attending Protestant services, he paid fines of about £22 million in today’s terms.) During that time he developed a scripturally based spirituality. A useful insight of Dr Young’s is that just because Tresham adhered to the “conservative” religion of Catholicism he was not intellectually unadventurous. In 1597 he was imprisoned in the Bishop’s palace at Ely. There he designed intricately symbolic painted devices for the long gallery. He had noted that crucifixes and the like which his fellow prisoners painted on their walls there were washed off or defaced by their warders. But coats of arms or inscriptions were left alone. The decorations by Tresham have not survived, but a manuscript giving details has. That is where Dr Young, in his paper in British Catholic History for October, finds evidence of gematria and Christian Cabbalistic notions. In 1593, during an earlier imprisonment at Ely, Tresham had a strange experience. His personal servant was reading to him a passage about proofs that there is a God from a book by Robert Persons (his copy survives). “There was upon a wainscot table at that instant three loud knocks (as if it had been with an iron hammer) given to the great amazing of me and my two servants.” Three again. And four years later he borrowed ideas from the Christian Cabbalist Pietro Colonna Galatino (1460-1540) for a device at Ely. It depends on the idea that adding the Hebrew letter shin to the tetragrammaton (yodh, he, waw and he, Yahweh, a name of God) produced a pentagrammaton signifying Jesus. Dr Young points out that this doesn’t really work in Hebrew. But it retained a symbolic value. So Tresham placed the letter shin in a triangle surrounded by the initial letters for the Hebrew words ehich asser ehich (as he spelt them), in Latin sum qui sum, “I am who I am”, the meaning given to Moses of the name of God in Exodus 3:14. The exercise might seem pointless today. But it was not despicable in its time. Dee wrote a whole book on a single hieroglyph of his own devising, relating to alchemy and astrology. Tresham’s enterprise, moored to scriptural revelation, was a devotional poem in miniature.