Roger Bacon on ciphers. Addendum to ‘Wheat from the Chaff’ post.


Of obscuring Art and Nature.

…. For that which all men, which wise, and the more noted men affirme is truth. That therefore which is held by the multitude, as a multitude, must be false ; I mean of that multitude, which is distinct from knowing men. The multitude, it’s true, agree with wise men in the more vulgar conceptions of their mind; but when they ascend to the proper principles and conclusions of Sciences and Arts, they much dissent (striving to get onely the appearancies in Sophismes and subtilties which wise men altogether reject.)

And this their ignorance of the properties and Secrets, makes the division from knowing men. Though the common conception of the mind, have all one Rule and Agreement with knowing men. Yet as for common things, they are of small value, nor enquirable for themselves, but rather for particular and proper ends.

The Reason then, why wise men have obscured their Mysteries from the multitude, was, because of their deriding and flighting wise mens Secrets of wisdome, being also ignorant to make a right use of such excellent matters. For if an accident help them to the knowledge of a worthy Mystery, they wrest and abuse it to the manifold inconvenience of persons and communities.

Hee’s then not discreet, who writes and Secrets, unlesse he conceal it from the vulgar, and make the more intelligent pay some labour and sweat before they understand it.  In this stream, the whole fleet of wise men have failed from the beginning of all, obscuring many wayes the abstuser parts of wisdome from the capacity of the generality.


[1] Some by Characters and Verses have delivered many Secrets.

[J.D.:This method is really advocating the use of jargon or of a vocabulary specific to a discipline that outsiders won’t typically understand).


[2] Others by ænigmatical and figurative words, as Aristotle sayes, (in lib. Secret.) ‘O Alexander, I shall disclose to you the greatest of Secrets, which it becomes you by divine Assistance to keep secret, and perfect the thing proposed. Take then the Stone, which is no Stone, which is in every man, and in every place, and in all times; and it shall be called the Philosophers Egge, and the Terminus Ovi’. And thus we find multitudes of things obscured in the Writings and Sciences of men, which no man without his Teacher can unvail.

[J.D. In this method, Bacon is recommending the use of a secret language known only to the writer and the reader. The language can use secret metaphors and phrases to represent other ideas and facts.]

[D:  less a ‘secret’ language than a private one, natural among persons with personal ties and/or shared experiences. ]


[3] Thirdly, They have obscured their Secrets by their manner of Writing, as by Consonants without Vowels, none knowing how to read them, unlesse he know the signification of those words. Thus the Hebrews, Caldees, Arabians, nay the major part of men do most an end write (Significata) their Secrets, which causeth a great obscurity amongst them, especially amongst the Hebrewes. For as Aristotle sayes in his fore-recited Book, God gave them all manner of Wisdome long before they were Philosophers: And all Nations had their Originals of Philosophy from the Hebrewes, as Albumazar in lib. Introductorii Majoris; and other Philosophers, with Josephus lib.I. & lib.8. Antiquit. makes it evident.

[J.D: Here, Bacon is advocating writing down messages using techniques from foreign languages like Hebrew or Arabic, which don’t use vowels in their written languages. This might be considered a form of shorthand].

{D: Bacon tried to study Hebrew, and may have encountered Jewish gematria and atbash, although these were regarded as aids to grasping the deeper significance in divine law and writings, a usage should be distinguished from secular uses for ciphers and cryptograms.]


[4] Fourthly, This obscuring is occasioned by the mixture of several sorts of Letters, for so the Ethnick Astronomer hid his knowledge, writing it in Hebrew, Greek and Latine Letters altogether. [note] Ethicus Astronomus fortasse. N. deest ergo Anglice dedi Ethnick. [i.e. Ethicus/Aethicus].

[J.D. Bacon is here advising using letter substitutions to obscure the spelling of letters in English or Latin. He suggests using Hebrew, Greek or Latin equivalents]

[D: for Aethicus’ alphabet see end of this page].


[5] Fifthly, This obscuring was by their inventing other letters, then those which were in use in their own, or any other Nation, being framed meerly by the pattern of their own fancy, which surely is the greatest impediment; yet this was the practice of Artesius in lib. de Secretis Naturæ.

[J.D.: In this method, Bacon is suggesting using characters that are not normal letters in the cryptogram. This is not unlike Edgar Allen Poe’s crytogram in The Gold Bug. Because at this point Bacon (and European in general) did not know anything about frequency analysis, Bacon sees this type of substitution as particularly difficult to solve.]

[D. The technique we call frequency analysis was among the techniques described by al-Kindi, an Iraqi mathematician of the 9thC AD, some of whose works were known in medieval Europe. His work on ciphers is entitled,  Risalah fi Istikhraj al-Mu’amma (‘Manuscript for the Deciphering Cryptographic Messages’).


[6], Sixthly, They used not the Characters of Letters, but other Geometrical Characters, which have the power of Letters according to the several Position of Points, and Markes. And these he likewise made use of.

[J.D. Here, Bacon is espousing substituting geometrical shapes for letters. Again, he thinks this will be more difficult to solve.]


[7] Seventhly, There is a greater Art of obscuring, which is called Ars Notoria, which is the Art of Noting and Writing, with what brevity, and in what manner we desire. This way the Latines have delivered many things. I held it necessary to touche at these obscurings, because it may fall out, I shall thorow the magnitude of our Secrets discourse this way, that I may help you so farre as I may.

[J.D. Finally, Bacon seems to be really advocating for the use of a true shorthand system here.]


compare with e.g.:

  • Tenney L. Davis (trans.), Roger Bacon’s letter concerning the marvelous power of art and of nature and concerning the nullity of magic …. together with notes and an account of Bacon’s life and work. (1923). Entry at Stanford University,   (here).

Bacon’s study of Hebrew.  The seminal study is:

  • Edmond Nolan, S. A. Hirsch, The Greek Grammar of Roger Bacon, and a Fragment of His Hebrew grammar.(1902)

On the distinction between secular cryptography and the use of atbash etc., Sternman’s paper reports rabbinical disapproval of secular esoteric speech and writing.

It should be noted that in every language there is the straightforward usage that the common person speaks, and there is a more sophisticated plane on which the ministers communicate. We have seen in the Talmud that within the Greek language (that has great stature as it may be used in writing holy books – as in Megilla 8b) there is a dialect called Greek Wisdom that the Rabbis prohibited ….. And as Rabbenu Hillel explained, this type of sophisticated secret dialect, which exists in any language, is prohibited. The ban is not only on the language of Greek (chochmat yevanit), but in any language.

quoted in: Baruch Sterman, ‘Jewish Cryptography’, paper (undated) available online as pdf at time of writing.

  • John Dooley, History of Cryptography and Cryptanalysis: Codes, Ciphers, and Their Algorithms. (2018)

Dooley devotes much space to the figure of John de Foxton, a copy of whose Liber Cosmographiae contains a cipher alhabet unknown from other sources.  Of this manuscript, J.B. Friedman says:

Among the treasures of Trinity College, Cambridge, is a compendium of popular science, the Liber Cosmographiae, made by the Yorkshireman, John de Foxton, in 1408. This volume is said in the colophon to have been given by the author, called « capellanus», to the brothers and minister of the Trinitarian house of Saint Robert at Knaresborough. … The manuscript has remained relatively little known since, though its contents and beautiful illustrations are of considerable interest to medievalists. One of the work’s most striking features is the enciphering of a of words by means of a substitution alphabet unlike any other known to us from the Middle Ages.

  • from: John Block Friedman, ‘The Cipher Alphabet of John de Foxton’s Liber Cosmographiæ’,  Scriptorium, Tome 36 n°2, (1982). pp.
    219-235. available online through the Persee site ( after you pass a test to prove you’re a human with fair eyesight.


Cipher alphabet of Bacon’s ‘Ethnic’ (Aethicus/Ethicus)