At the completion of the tale of Saint Cecilia, a Canon, riding a dilapidated old hack, and his Yeoman, on an even worse hack, ride up to the pilgrims. The Host welcomes them and asks whether either has a tale to tell. The Yeoman answers immediately that his master knows much about mirth and jollity, and then he begins to tell the secrets of their trade and all he knows about alchemy. Seeing that the Yeoman plans to tell everything, the Canon slips away in shame.
The first part of the Yeoman's tale is autobiographical: He explains that once he had good clothes and a comfortable living, that he and the Canon are alchemists, and that he is so in debt because their attempts at alchemy always fail. He then tries to explain their occupation, their failed attempts at alchemy, and their elusive search for the Philosopher's Stone. The tale itself comprises the second part of The Canon's Yeoman's Tale.
A canon who practices alchemy borrows a mark from a priest. In three days time, the canon returns the mark and offers to reveal a couple of his discoveries. He sends for some quick silver and, by tricks, makes the priest believe that he turned the quick silver into real silver. Unaware of the trick, the priest is very pleased. Three times the canon tricks the priest, each time "turning" a less valuable object (quick silver, chalk, and then a twig) into silver. The beguiled priest buys the secret from the canon for 40 pounds, and the canon promptly disappears. The Yeoman ends his tale with a broadside attack on the subject of alchemy and a conglomeration of all the ridiculous terms used by alchemists.
Just as The Second Nun's Tale closes, two strangers, a church canon and his servant (or yeoman), gallop up to the pilgrimage and join it. Before long the Yeoman reveals — half by accident — that the Canon is a thieving alchemist. The Canon flees the company, thereby essentially acknowledging his rascality, and the Yeoman renounces the practice of alchemy. He explains this renunciation to the pilgrims, and to himself as well, in two ways: first, in Part I of his tale, by a discussion of the pride of such alchemists as his master, an intelligent man whose sharp, unreasonable self-delusion leads him into cruelly deceiving other men; and then in Part II, which is a parable that implicitly condemns alchemy on the grounds that it makes men prey to exploitation by all sorts of rascals.
Because neither the Canon nor the Canon's Yeoman is presented in The Prologue, most authorities agree that this prologue and tale were written well after The Prologue.
During the Middle Ages, people believed that certain base metals lay in the ground for many years and, ultimately, became purer higher metals. They also believed that an alchemist could accelerate this process, turning a base metal (such as lead) into a precious metal (such as gold) in moments. Alchemy was considered a science by which this transmutation occurred. In truth, alchemy was pure charlatanism with the alchemist being the ultimate charlatan — a superb pretender to knowledge or skill.
Part I of the tale is a rogue's confession (compare it with the prologues of the Pardoner and the Wife of Bath). Part II is the story of how an alchemist dupes a poor, credulous priest. The sin of alchemists, the Yeoman says, is intellectual pride, which can result in a substitution of reason for faith, which is exactly what happens to the priest in Part II. On the basis of relatively little evidence of the alchemist's honesty, the priest forgets his vows and comes to accept the alchemist's pretensions.
canon a member of a certain religious order.
Philosopher's Stone an imaginary substance sought by alchemists, who believed it to be capable of transmuting base metals into precious ones.
Arnold reference to Arnoldus de Villa, a fourteenth-century French physician, theologian, astrologer, and alchemist.
Luna . . . Sol moon and sun.
chimica senioris zadith tabula here, attributed by Chaucer to Plato but in the original publication (Theatrum Chemicum, 1695), it was attributed to Solomon.
ignotum per ignotius Latin, meaning "an unknown thing (explained by) a more unknown thing." In other words, to explain something difficult by using something even more difficult.