Johannes Trithemius

Trithemius was abbot of Sponheim, a serious historian, and the builder of one of the great libraries of his day. He was also the author of the Steganographia, composed around 1499, which describes the transmission of messages over distance by conjuring planetary angels, complete with the names of the spirits and the invocations to address to them.

It circulated in manuscript for a century, ruined his reputation while he lived, was printed in 1606, and was placed on the Index in 1609, where it stayed until 1900.

The twist is that a large part of it is cryptography. The angel names and the barbarous invocations in the first two books are ciphertext: the message is concealed inside the conjuration, and the Clavis printed alongside the 1606 edition already said so. The third book resisted much longer and was solved only in the 1990s, Thomas Ernst published the solution in 1996 and Jim Reeds reached it independently and published in Cryptologia in 1998. Trithemius's other major work, the Polygraphia, is straightforwardly a cryptographic manual and is one of the founding texts of the discipline.

The tempting conclusion, that the magic was only ever a cover for the codes, is too neat, and the specialist literature does not support it. Noel Brann's study argues that Trithemius held a genuine magical theology, and that the cryptography and the angelology were not alternatives but a single project: a Christian science of hidden communication in which cipher and spirit were both instruments. His De septem secundeis is plain angel-driven historical prophecy with no cipher in it at all, assigning successive ages of the world to seven planetary intelligences. He was not hiding a secular mind behind a magical mask; he had both.

Two episodes frame Trithemius better than the cipher book. The first is a forgery. To give the abbey of Sponheim and the German nation a deep past, he cited a chronicler named Hunibald, supposedly writing near the time of the Franks' Trojan origins, and wove from him a circumstantial early history that impressed the emperor Maximilian himself. No Hunibald manuscript has ever existed; when pressed to produce it, Trithemius could not, and his reputation among humanist historians never recovered.

The scholar who made Sponheim's library one of the wonders of Germany, roughly two thousand volumes assembled on an abbot's income, was also willing to manufacture the sources his shelves lacked. The second episode is a visit. In 1510 the young Heinrich Cornelius Agrippa came to him and showed him the draft of De occulta philosophia, the book that would organise Renaissance magic for a century. Trithemius read it quickly, approved, and sent the famous covering letter of advice: communicate vulgar secrets to vulgar friends, but higher secrets only to higher friends, speak of things public publicly and of exalted things secretly. Agrippa printed the letter with the book, and the abbot's rule of discretion became part of the charter of the Western esoteric tradition: learned magic as something to be written, but written guardedly, for the few. Forger, librarian, cryptographer and cautious patron, he taught the occult its manners.