Late in his life, early in the 5th century BCE, Confucius complained that he was getting old, and gave his reason: it had been a long time since he last dreamed of the Duke of Zhou (「久矣，吾不復夢見周公」). The Duke, regent in the early Western Zhou and the model statesman of Confucius's own tradition, had been dead for more than five hundred years. Roughly six hundred years later, the Han writer Wang Fu (王符) filed that remark under a theory of dreams: Confucius thought about the Duke's virtue all day, so he dreamed of him at night. Some eight hundred years after that, a dream book carrying the Duke's name appears in manuscripts from Dunhuang, and later in a bibliography of the Song dynasty's books.
No dream book can be traced to the Duke of Zhou. His name most likely reached the genre through Confucius's dream, not through anything the Duke wrote, and "going to see the Duke of Zhou" (夢周公) is still an ordinary way to say someone has fallen asleep. The 周公解夢 you find online is a third thing again: an undated folk compilation, copied from site to site, whose copies do not agree with each other.
The copies on the web
The text most sites call 「原版周公解夢」, the original edition, is a list of short lines in 27 sections, each line a dream and a verdict: 「蛇入懷中生貴子」, a snake entering your bosom means a noble son. Nobody we could find has identified the printed edition it was copied from, and the sites that present it as the original do not say which one they mean.
We measured how well two public copies agree. Our own dream dictionary used to carry 952 lines, taken from a small code repository with no stated source; 938 of them appear word for word on one commercial fortune-telling site, including its garbled section titles. We then compared those 952 lines against the transcription on Chinese Wikisource, which is itself marked as not proofread (未校對). Six hundred and twenty-two lines matched exactly. The other 330 differed, most by one or two characters, and some of those characters reverse the verdict.
One line about a sick person gives opposite outcomes in the two copies. Doves call and a woman has quarrels (鳩鳴…口舌) in one, and doves and a woman's joy (鳩鴿…有喜) in the other. Crickets chirping bring a minor vexation (小惱) or minor good fortune (小吉). Losing shoes (失履) becomes obtaining them (得履). A section title that means inner and outer coffins (棺槨) had become 館郭 in the site copy, and our old English translated it as "mansions". Neither copy is authoritative: Wikisource's transcription has corruptions of its own, such as 鐘豉 where the sense needs 鐘鼓, drums and bells.
The same method, two editions of an oracle text compared character by character, is set out in our guide to counting the hundred temple lots. Here it turns up something plainer: the dream book most people mean by the name has no fixed text.
Our Zhou Gong dream dictionary has since been rebuilt on the Wikisource transcription, revision 7907671, all 988 lines in 27 sections, with each line labelled as the Wikisource line it is and the transcription's own slips left uncorrected. Its English is a draft that has not been reviewed by a specialist, and the page says so. The text also foretells deaths and illnesses; the tool keeps the 22 lines that predict a death, because they are part of the text, and presents every line as what the book says rather than what a dream means. There is no evidence that dreams predict events, and researchers do not agree on what dreaming is for: in the words of the neuropsychologist Mark Solms, quoted in a 2010 review by Nir and Tononi, "the biological function of dreaming remains unknown".
宋史·藝文志
The first time a catalogue lists a book by this name is in the bibliography of the History of Song (宋史), compiled in 1343–45 from the Song court's own catalogues. In its section on divination it records 「《周公解夢書》三卷」, a dream book of the Duke of Zhou in three scrolls (卷), between other dream books by named authors.
The earlier official bibliographies list dream books too, and none of them carries the Duke's name. The Han bibliography has two, credited to the Yellow Emperor and to the astronomer Gan De. The Sui bibliography has eight, including a two-scroll 解夢書, a book for interpreting dreams. The two Tang bibliographies list a handful more. The Duke first appears in the Song listing, and whether that book is the same text as anything that survives cannot be shown: the listing gives a title and a length, nothing else.
Pelliot chinois 3908
The copies that do survive are older than that listing. The library cave at Dunhuang, sealed around 1000 CE and opened in 1900, held about fifteen manuscripts on dream interpretation. The only complete copy of a Duke of Zhou dream book among them is Pelliot chinois 3908 in the Bibliothèque nationale de France: a small booklet of 20 leaves, 16.7 by 12.5 centimetres, which the library dates to the 10th century.
Its title is 新集周公解夢書, the newly compiled Duke of Zhou dream book, and its closing title calls it 周公備急解夢書一卷. After a preface it sets out dreams and their meanings under 18 headings, then three headings on when a dream happens and one on how to ward off a bad one: 22 sections in all. A fragment in London, Stein 5900 in the British Library, preserves the start of the same text.
That structure is not the web text's: 22 sections against its 27. The name carried on; the book behind it changed.
漢書 and 潛夫論
Dream reading itself is far older than any book with the Duke's name. The Book of Odes (詩經), the oldest Chinese poetry anthology, has a diviner reading dreams of bears as the sign of a son and snakes as the sign of a daughter (「維熊維羆，男子之祥；維虺維蛇，女子之祥」). In the web text the snake has become a noble son. The Rites of Zhou (周禮), a text of about the 3rd century BCE that describes an idealised Zhou government, prescribes an office of dream diviners and six kinds of dream.
By the 1st century CE the Han historians could survey the whole practice. The bibliography chapter of the History of the Han (漢書·藝文志) says that of all the kinds of divination, dreams were the greatest (「眾占非一，而夢為大」), and in the same passage warns against those who neglect their own conduct to fret over omens (「傷其舍本而憂末」).
Wang Fu, writing in the 2nd century, sorted dreams into ten types in his Comments of a Recluse (潛夫論). One is the "inverse" dream (反), which means the opposite of what it shows; the web text still reads dreams that way, and in it loud weeping brings joy. Another is the dream of what you thought about by day (「晝有所思，夜夢其事」), an ancestor of the proverb 「日有所思，夜有所夢」, which a 17th-century story already calls a common saying. Confucius's dream of the Duke he filed under a third type, the dream of concentrated thought (意精之夢).
論語·述而
The sentence at the start of this guide is in the seventh book of the Analects (論語·述而): 「甚矣，吾衰也！久矣，吾不復夢見周公！」, "How far I have declined! It is long since I dreamed of the Duke of Zhou." It is about Confucius dreaming of the Duke, not the Duke interpreting anyone's dreams. The step from that sentence to a book title is an inference. Wang Fu shows that by the 2nd century the Duke already stood for dreaming, but no source we read says the book was named for him on that account.
Wang Fu also left the most useful advice for anyone consulting a dream book. Dreams can be vivid and mean nothing, he wrote, or faint and come true, so they should not be relied on alone to decide things (「故亦不專信以斷事」). He followed with a sharper point: 「是故占夢之難者，讀其書為難也」. The hard part of reading dreams is reading the book.
