Chaucer drew on an astonishingly vast repertoire of optical and medical material as he created the Merchant's Tale. Optical themes such as the treatment of visual deception employed by May and Chaucer's knowledge of the medieval tradition of perspectiva, especially as it was represented in specialized scientific works, encyclopedias, vernacular poetry, and sermon exempla, have been examined in detail by Peter Brown.(FN1) Another optical theme--January's moral and spiritual blindness--has been examined to varying degrees by nearly all who have written on the tale.(FN2) The etiology of January's physical blindness, however, remains to be explored.
    Scholarship has not failed to point out January's moral blindness and his visual deception, but Chaucer clearly understood the causes of physical blindness as well.(FN3) Allusions in the tale suggest that the Middle English translation of Benvenutus Grassus's De probatissima arte oculorum, or another medical text like it, served as a source for Chaucer's knowledge on blindness.(FN4) If Chaucer did not know De probatissima arte oculorum, his optical knowledge could have come from Guy de Chauliac's Cyrugie, which offers a detailed explanation of the causes and cures of cataracts, or even from Bartholomaeus Anglicus's De proprietatibus rerum. While Bartholomaeus is useful and affirms what can be said using De probatissima arte oculorum, Benvenutus Grassus offers, as a practicing and "a profunde phycycyane" (49), important details about eye maladies and their cures that an encyclopedist cannot. Given its detail, Benvenutus's text is particularly useful both for discussing January's (moral) blindness and for revealing Chaucer's surprising ophthalmological knowledge as well.
    Benvenutus Grassus, also known as Benvenutus of Jerusalem, lived at the end of the thirteenth century, traveled extensively in Italy and probably into North Africa and France, and may have taught at Montpellier.(FN5) Though he is not mentioned by the Salernitans he claims to know, his name and methods of curing are mentioned by Jean de Yperman in a treatise dated 1328.(FN6) The earliest manuscript referencing his work is most likely that of a Provengal translation from the thirteenth century, but there are four existing Middle English translations of his work, the earliest in Oxford, Bodleian Library MS Ashmole 1468, a text containing three manuscripts, which are worthy of note. The first text dating from the early fifteenth century contains the work by Benvenutus and precedes Guy de Chauliac's Cyrugia. This manuscript also contains a treatise on anatomy based on both Guy de Chauliac and Henri de Mondeville; medical recipes; and a medical vocabulary in English and Latin. Avicenna's book IV of the Canon dealing with fevers and a medical treatise in Latin make up the second manuscript, while a copy of Piers Plowman is the third in the bound text.(FN7)
    As a physician, Benvenutus relies heavily on Galen's treatment of over a hundred illnesses affecting the eye and the humoral theory that was at the heart of medical treatment throughout the Middle Ages. Much of his knowledge of Galen must have come by way of Hunain Ibn Ishak, better known in the West as Johannitius, who studied medicine under Yuhanna ibn Masawaih, and who wrote two compositions on ophthalmology: the Ten Treatises on the Eye and the Book of the Questions of the Eye. As David C. Lindberg has noted, these treatises "represent the penetration of Galenic theories into Islam."(FN8) Indeed, it was chiefly through Hunain that medieval ophthalmologists in the West had access to Galen. As a result of this influence, Benvenutus not only accepts the concept that the body is composed of four humors, but also that the brain contained three ventricles. Benvenutus, nevertheless, simplifies Galen, as Eldredge notes, reducing hundreds of eye illnesses to a limited number. He gives seven cataracts, seventeen diseases resulting from an imbalance of one or another of the four humors, two illnesses that may follow from the last of the melancholy ailments, and finally a number of injuries affecting the eye. He ends with a collection of recipes for eye medicines and a diet recommended for those recovering from illness or injury to the eye. Benvenutus's discussion of diet especially pertains to Chaucer's description of January's blindness in the Merchant's Tale.
    Sixty-year-old January has followed his bodily appetite for women into old age. As the Merchant explains, January

       lyved in greet prosperitee;
And sixty yeer a wyflees man was hee,
And folwed ay his bodily delyt
On wommen, ther as was his appetyt,
As doon thise fooles that been seculeer.

    (IV1247-51)(FN9)
    On his "pittes brynke" (IV 1401), he considers the state of his soul, but hopes to continue his "blisful lyf" (TV 1259)--now to be sanctioned by the "hooly boond" of marriage (IV 1261)--until he dies. Not only does he want to save his soul through marriage, but he also wants a young wife, especially one on "which he myghte engendren hym an heir" (IV 1272) and who will keep him when he is "syk" (IV 1289). The irony surfaces, indeed continues, when he explains that a man should

Take hym a wyf with greet devocioun, By cause of leveful procreacioun Of children to th'onour of God above

    (IV 1447-49),
    or "leccherye eschue" (IV 1451) by living in "chastitee ful holily" (IV 1455), but then goes on to deny flatly that he is motivated by these precepts: "that am nat I" (IV 1456).
    If there is any appeal in January to the audience or reader, it can only be that he is a sick old man, physically and mentally, and that he fulfills the role of the senex amans. The fact that he is mentioned as being sick is certainly no coincidence, for he will suffer blindness at the end of the tale, which is part of the irony needed for the tale's success. Chaucer does not, however, let January's blindness appear without establishing causes for it; thus January's comment on needing a nurse when he is sick is all the more pointed. That is, January's blindness is no "sodeyn hap" or a result of Fortune's instability (IV 2057), as the Merchant would have us believe.(FN10) Contrary to the Merchant's assertion, Benvenutus's text on eye maladies provides a basis for the diagnosis that January's blindness results in large part from his appetite for food and sex, appetites stressed from the beginning of the tale and which are important for understanding the irony within the tale.
    According to Benvenutus, there are seven types of cataracts, four of them curable and three of them incurable. While three of the curable cataracts do not require a special diet, at least one type of cataract does, as do the three incurable types:

[N]oon of Pies iiij curable cateractes yt nedyth to doon from clene metys abstynence, as I haue prouyd by experyence, saue oonly yn the thyrde spyce, where neuerthelesse yt behouyth alwey to haue conforatiuus and neutrytyuus of the vysible spirytyn the eyon. (58) A patient who loses his sight from this type of cataract can "recouere" his sight if "it dure not long yn that astate" (56), but other restrictions must be made on the patient's appetites for food and for sexual relations. The patient should eat hot and moist digestible food to engender "good blode," but he must not eat "contrarius metys" or "cowes fleshe, ghetys fleshe, and eelys, and such oþer, and specyally of rawe onyoins, for they be specyally contrarius" (57). In the winter the patient must not drink warm wines. And a patient must "abstene . . . from commenyng of women, nor let nat hym corn in no bath nor stew" (57).

    While January is not physically blind in the beginning of the tale, he does, nevertheless, appear to be leading himself to blindness throughout. Benvenutus explains that excess food and drink cause the fourth type of curable cataract: "it ys comunly gendryd of exces meete and drynk yndegest, and also of gret labour and sumtyme humurs malencoly" (53). Early in the tale we learn that January has followed his "bodily delyt / On wommen" for all his life (IV 1249-50), and while we do not see him gorge himself on food and drink until his wedding feast and immediately before he goes blind, he does use the language of flesh and meat to describe his lusty appetite for women. He desires a young wife:

"Oold fissh and yong flessh wolde I have fayn. Bet is," quod he, "a pyk than a pykerel, And bet than old boef is the tendre veel. I wol no womman thritty yeer of age."

    (IV 1418-21)
    According to Benvenutus, January's lifestyle would certainly prevent the recovery of a blind man or one with cataracts, especially one like January who admits he has his "body folily despended" (IV1403); his gluttonous lifestyle can certainly lead to an eye malady as well. On the day of the wedding feast, for example, January is "dronken in plesaunce" (IV 1788), and all those in attendance were "ful of joye and blisse" (IV 1712), not only because of music but because "Bacus the wyn hem shynketh al aboute" (IV 1722). Married under Taurus, May emerges from "hir chambre" several days after the wedding night with the moon in the zodiacal sign of Cancer (IV 1885-88).
    January can hardly be faulted at this point for failing to follow Benvenutus's advice to abstain in the winter from "hoote wynes yn whych be put sawge and rewe" (57). While January "drynketh ypocras, clarree, and vernage / Of spices hoote" (IV1807-8), his wedding takes place not in the winter but in the late spring or early summer season, and while the wine might be "hoote," he does not drink wine with "sawge and rewe," but rather strong spiced and sweetened wine: "ypocras, clarree, and vernage." January is drinking excessively, however, which Benvenutus warns against, especially for a senex like January. Old men, Benvenutus notes, should drink "wyne medlyd [with] water" (55) and cannot be bled like those that "be yong" (60). Nevertheless, January drinks his spiced wine to increase his blood and heart for his anticipated wedding night of sexual bliss, and he also drinks "many a letuarie" that "Constantyn" the African recommends in his medical text De coitu (IV 1810-11) as an aphrodisiac. No doubt this "letuarie" is what will make his "lymes stark and suffisaunt / To do al that a man bilongeth to" (IV 1458-59). The wedding night, however, is no night of bliss for poor May. She sadly notices that his "slakke skyn about his nekke shaketh" (IV 1849), and January refers to himself as a "werkman" that does not "bothe werke wel and hastily" (IV1832-33).
    January "laboureth" a great deal during his sexual encounter with May (IV 1842), and because he "labors" so heartily as a senex, he is setting himself up for blindness here, too.(FN11) Benvenutus explains that the fourth type of curable cataract is not only caused by "exces meet and drynk" but "also of gret labour and sumtyme hurmirs melencoly" (53). January is so exhausted from his sexual bliss, in fact, that he must eat some bread soaked in wine.
    January's overindulgence is revealed again several days after the wedding, when he remembers his squire Damyan. He bids May attend to Damyan "[b]ut after mete" (IV 1913), or after a meal. This command is repeated when he tells her "[a]t after-mete" to attend Damyan (IV 1921). Little seems more important to January than eating and sexual pleasures; thus he is indeed setting himself up for blindness. In spite of what the Merchant tells us, then, it comes as no surprise to the trained observer that January is "biraft hym bothe his yen" (IV 2067). January weeps and wails his loss of sight, but while it appears that he is weeping for the loss of his vision, he is also weeping because of jealousy. If he cannot keep an eye on his young bride, then "his wyf sholde falle insomfolye" (IV 2074).(FN12)
    January does not appear to try to cure his blindness in the tale itself. His blindness seems to be of the type Benvenutus Grassus would describe as being curable only by God:

I wyll that ye knowe all thyes maner of cateractes been vncurable, less þan God cure þem, ffor the neruys obtyk be so opylate, that ys such maner of synewes ben so stoppyd and mortifyed, þat no medycyn may helpe yt. (58)

    Certainly, January's blindness would fall into the category of those maladies curable only by God since he appears unable to practice the self-control needed according to Benvenutus. Indeed, it is the god Pluto who restores his eyesight in time for him to see his wife copulating in the pear tree with Damyan.
    While the tale itself dictates that his blindness remain until he is cuckolded, it is interesting to read the pear tree scene in the context of Benvenutus's text. When January is hindered from having sexual relations with his wife in the garden because she would rather ascend the tree for some fruit, he is unwittingly fulfilling Benvenutus's command to abstain "from commenying of women" until patients "recouere perfysste helth" (92). Refraining from sex, even for that moment, has been his cure. Given that May is not having intercourse with January but rather with Damyan, this approximates what May claims as her defense:

I have yow holpe on bothe youre eyen blynde. Up peril of my soule, I shal nat lyen, As me was taught, to heele with youre eyen, Was no thyng bet, to make yow to see, Than strugle with a man upon a tree.

    (IV 2370-74)
    The end of the tale makes completely clear, as Peter Brown has noted, that May draws on her knowledge of optical illusion and perspective to persuade her husband that what he physically sees is unreal. She was not copulating in the tree with Damyan, she says: January has been beguiled because his recovered sight was not "ysatled" a while (IV 2405).
    Brown has observed that Bartholomaeus Anglicus deals with causes of defective vision and blindness in the seventh book of De proprietatibus rerum. The causes of blindness offered by Bartholomaeus correspond in large part to those in Benvenutus. He explains, for example, that with old age the "yssen wexen dymme, and þanne þey haueþ defaute of sisst, and at þe last þe vertu of sisst failleþ and þey lesiþ al here sisst." Similarly, food and drink affect vision: it "waxiþ and wayneþ by diuersite of mete and of drinke."(FN13) All of these causes match the description that Chaucer gives us of January as over sixty, a bon viveur, and an immoderate womanizer. Nevertheless, Benvenutus's text offers far more in the way of optical details and is useful for this reason alone.
    Clearly several optical themes are at work in Chaucer's Merchant's Tale. Peter Brown's discussion of optical illusion established that the analogues to be found in Alhazen, Witelo, and Bartholomaeus Anglicus should not be disregarded. What has been established here is that Chaucer is drawing on a great deal of other optical material previously unaddressed, namely that of ophthalmology. Chaucer understood the causes of physical blindness as explained by authors such as Benvenutus Grassus. When taken together, then, optical themes help reinforce the central issue of inner blindness and call for the reader's own enlightenment.(FN14) Whereas January's health deteriorates in the tale, the reader's should increase. As a result, Chaucer's optical knowledge "teaches his audience to see,"(FN15) in a moral as well as a physical sense, and thereby adheres to Benvenutus's dictates regarding healthy vision.
ADDED MATERIAL
    James M. Palmer
    Prairie View A&M University
    Prairie View, Texas
    [email protected]
    I would like to thank Ann Astell, Glending Olson, and the anonymous readers for The Chaucer Review for their helpful comments on previous versions of this paper.

Footnotes
1. Peter Brown, "An Optical Theme in The Merchant's Take" in Studies in the Age of Chaucer, Proceedings, 1984: Reconstructing Chaucer, ed. Paul Strohm and Thomas J. Heffernan (Knoxville, Tenn., 1985), 231-43, explains Chaucer's indebtedness to scientific explanations of optical illusion and focuses on the final episode in the tale. Recently Michelle Kohler has examined how the logic of "seeing" a lie develops within certain fabliaux and can illuminate the force of language as well as the absurdity central to their humor ("Vision, Logic, and the Comic Production of Reality in the Merchant's Tale and Two French Fabliaux," Chaucer Review W [2004]: 137-50).
2. Statements such as the following appear to certain degrees in much MerT scholarship. Jessica Cooke comments that January is "symbolically blind for most of the tale" ("Januarie and May in Chaucer's Merchant's Tale," English Studies 78 [1997]: 407-16), while Angela M. Lucas comments, "With a mind clouded by ignorance of himself and of eternal values, Januarie will always see 'through a glass darkly,' never accepting that his marriage is not, and cannot be, the paradise he had imagined it to be. Januarie is eventually given vision which forces him to a knowledge of his situation which he turns away from and forgets" ("The Mirror in the Marketplace: Januarie Through the Looking Glass," Chaucer Review 33.11998]: 123-45, at 139). Lucus goes on to say, "Januarie's assumption that May will conform to the image which he has formed of her in the mirror of his mind indicates the failure to move beyond self-love, as well as the lack of inner vision" (140). Lucus's comments can be contextualized within an optical theme, that of mirrors both real and figurative.
3. Although Chaucer does not mention medical texts in MerT, other than that by Constantine the African, in SqT le mentions Alhazen and Witelo, both of whom were authorities on optical science (rather than ophthalmology) and are mentioned along with Aristotle. In that tale they are referenced as authorities of "mirours and of perspectives" in particular (V 232-34). Alhazen (Abu Ali al-Hasan ibn al-Hasan ibn al-Haytham, ca. 965-ca. 1039) was the most significant figure in the history of optics between antiquity and the seventeenth century. On his influence and theory of vision, see David C. Lindberg, Theories of Vision From Al-Kindi to Kepler (Chicago, 1976), 58-86. Witelo (ca. 1230/35-ca. 1275) wrote especially on perspectiva (Lindberg, 116-21). That SqT follows MerT in the Ellesmere Manuscript is appropriate because May is a master of persuasion based on her scientific knowledge of perspective.
4. Benvenutus Grassus, The Wonderful Art of the Eye: A Critical Edition of the Middle English Translation of His De probatissima arte oculorum, ed. L. M. Eldredge (East Lansing, Mich., 1996), 23. All citations of Benvenutus are from this edition. For a translation of Benvenutus's Latin work, see Casey A. Wood, trans., Benevenutus Grassus of Jerusalem, De Oculis, erorumque egritudinibus et curis (Stanford, 1929). Peter Brown suggests that Chaucer may have known Bartholomaeus Anglicus's seventh book of De proprietatibus rerun, which also deals with causes of defective vision and blindness. While this may be the case, Benvenutus offers a more detailed explanation of blindness and its causes. Utilizing Benvenutus allows, furthermore, for a greater exploration and explanation of Chaucer's medical allusions.
5. Eldredge, "Introduction," in Benvenutus, The Wonderful Art, 4.
6. Eldredge, "Introduction," in Benvenutus, The Wonderful Art, 4.
7. Eldredge, "Introduction," in Benvenutus, The Wonderful Art, 20-22. Eldredge suggests that these manuscripts were probably first bound together in the seventeenth century, though not at Ashmole's request as his arms are not stamped on the binding.
8. Lindberg, Theories of Vision, 34. In his "Introduction" to Benvenutus's Middle English translation, Eldredge suggests that Benvenutus's knowledge of Johannitius (Hunain) "seems to have been derived exclusively from the Ysagoge, a brief commentary on Galen" (11). The Ysagoge was found as part of the Articella, one of most important medical textbooks of the later Middle Ages. For a brief introduction to optical theories, see Dana E. Stewart, The Arrow of Love: Optics, Gender, and Subjectivity in Medieval Love Poetry (Lewisburg, Pa., 2003).
9. All citations of Chaucer are from The Riverside Chaucer, ed. Larry D. Benson, 3rd edn. (Boston, 1987).
10. Chaucer's presence in this tale is revealed through the tale's medical details, which in many ways destabilize the Merchant's own authority. An analysis of Chaucer's medical allusions serves to distinguish in some ways the narratorial and authorial points of view in the tale. Robert R. Edwards has also noted, in a different context, this destabilizing element in the tale, arguing that as "the Merchant elaborates his story and so discloses his characters, elements of his story suggest alternatives to his vision" ("Narration and Doctrine in the Merchant's Tale," Speculum 66 [1991]: 342-67, at 343). The central question here, according to Edwards, is the "disjunction between the narrator and his materials" (366).
11. Although Benvenutus is not addressing sexual labor, Chaucer is clearly stressing the physical labor January experiences during the sexual act.
12. It is interesting to note that Benvenutus explains that tears are caused by different parts of the body: "þere is different causes of teres whych spryng out of the ouer eylede and whych spryng oute of the nether, ffor tho whych come out of the nether eyelyde proceden from the hert, eyther for sorrow, drede or smart, and be caused by a maner of vyolence. But they be not durable nor abydyng, for when the cause [Perof cesyth Pei sesyn. But the teres whych cum oute of the hoole of the ouer lyd of the ey proceden from the brayn and be causis of sum corrupcion of habundans of superfluytee of humors, and her course ceceth not but yf the mater be pourgyd and hopen wyth oure electuaryes and cautareyes, lyke as we haue tau3th beforne" (The Wonderful Art, ed. Eldredge, 85). Since January "wepeth and he wayleth" from the "fyr of jalousie," his tears come from the heart and not the brain (IV 2072-73). Chaucer even reveals that January's jealousy "So brente his herte that he wolde fayn / That som man bothe hire and hymn had slayn" (IV 2075-76). Thus, these tears are tears of real emotion. Similarly, Gilbertus Magnus explains that tears are caused from internal or external things: "Weping of yssen comeþ oþirwhiles of enchesons wipouteforþ, as of smokis, or of wyndes, or duste, or of a stroke. Oþirwhiles it comep of withyn, as of ioye, or of sorow, or of angir, or of plente of humours in þe heed, as of feblenes of þe veynes þat ben in þe ysse" (Gilbertus Anglicus, "The Middle English Gilbertus Anglicus from Wellcome MS 537," in Faye Marie Getz, ed., Healing and Society in Medieval England: A Middle English Translation of the Pharmaceutical Writings of Gilhertus Anglicus [Madison, Wisc., 1991], 57).
13. On the Properties of Things: John Trevisa's Translation of Bartholomaeus Anglicus, De proprietatibus rerum: A Critical Text, ed. M. C. Seymour et al., 3 vols. (Oxford, 1975-88), 1:364. These specific passages from Bartholomaeus Anglicus are noted in Brown, "An Optical Theme," 239.
14. The role of the eyes and the ymaginacioun or fantasye for January, and even for Damyan when he shows signs of lovesickness, offer further proof of Chaucer's knowledge of medieval optical and medical theory. For a discussion of sight as part of knowledge, see Norman Klassen, Chaucer on Love, Knowledge and Sight (Cambridge, U.K., 1996), especially 39-74; and Carolyn P. Collette, Species, Phantasms, and Images: Vision and Medieval Psychology in The Canterbury Tales (Ann Arbor, Mich., 2001).
15. Linda Tarte Holley, Chaucer's Measuring Eye (Houston, 1990), 21.