At the end of the fourteenth century, John Mirfield (d. 1407), chaplain of the hospital of St. Bartholomew in Smithfield, London, produced two Latin encyclopedias, the Breviarium Bartholomei, dedicated to bodily health, and the Florarium Bartholomei, dedicated to spiritual health. In a chapter of the Breviarium entitled ‘De signis malis’, Mirfield lists a plethora of methods available to a physician to predict the life or death of a sick person, and includes an experiment to prognosticate life or death using the numbers that correlate to the letters of personal names: ‘Take the name of the patient, the name of the messenger sent to summon the physician, and the name of the day upon which the messenger came to you; join all their letters together, and if an even number result the patient will not escape, if the number is odd then he will recover’. 
Mirfield, then, advocates the prediction of life or death by recourse to number-letter divination. However, in the Florarium, talking about the kinds of magic and divinatory practices to be avoided by those seeking spiritual health, Mirfield copies verbatim a passage from Gratian's Decretum, which states that the prediction of the life or death of the sick by using ‘certain numbers of letters’ is nothing short of ‘Pythagorean necromancy’ and is therefore illicit.  Whether or not Mirfield was aware of this contradiction between his two works is not known, but the incident is nevertheless a neat illustration of the borderline status of this sort of predictive method – it is at the same time both licit medicine and illicit divination. In late medieval England, most educated physicians were, like Mirfield, clerics. Anyone who had completed a medical degree was obliged to have taken minor orders, at the very least, before they could receive a university education, and many medical students went on to take major orders.  Additionally, many medical practitioners were also monks, who may or may not have attended university.  This makes the dual nature of the ‘Sphere’ even more interesting, since the clerical status of many medical practitioners may have made them all the more aware of the dangers of making a prediction in this way.
This article will examine the evidence for the ‘Sphere of Life and Death’ – probably the most popular method of numerological prediction in late medieval England judging by the sheer number of surviving manuscripts – as a legally dubious technique of divination, by looking both at general condemnations of the divinatory arts, and specific condemnations of this device in canon law, pastoral manuals and theological tracts. It will then examine the manuscript evidence for the ‘Sphere’ as an item of interest to, and used by, the learned physician in later medieval England. The author hopes to demonstrate that the categories of ‘licit’ and ‘illicit’ break down when we examine items such as the ‘Sphere of Life and Death’.
The ‘Sphere of Life and Death’ – hereafter referred to as the ‘Sphere’ for brevity – is a short prognostic device found in a range of medieval manuscripts. For the definition of ‘prognostic’ used here the author is indebted to László Sándor Chardonnens, who states that a prognostic is ‘a codified means of predicting events in the life-time of an individual or identifiable group of individuals, using observation of signs and times, or mantic divination’.  Within this category of prognostics, the ‘Sphere’ is an example of divination, belonging to the sub-category of onomancy.  ‘Divination’ is the prediction of future events through the interpretation of signs, and ‘onomancy’ is a type of divination that seeks to predict the future by using the numbers that correlate to the letters of an individual's name. The ‘Sphere’, surviving in many redactions in the later middle ages, circulated in the ancient world in Greek and Syriac manuscripts – and possibly Arabic and Hebrew as well. A Greek example attributed to the ancient philosopher Democritus is found in Leiden Papyrus V, a fourth-century C.E. papyrus containing a host of magic and divinatory spells,  and a Syriac version is present in a twelfth-century manuscript translated by E. A. Wallis Budge, whose contents have ancient roots.  The ‘Sphere’, then, entered the Latin West from different cultures and languages, which partly explains the five different redactions present in early medieval manuscripts.
The ‘Sphere’ is a circular, square, rhomboid, scroll-shaped or tabular diagram, with varied accompanying texts. It is used to predict the outcome of a variety of temporal events, usually whether a sick person will live or die. It also variously claims to predict whether or not a combatant or general will win a duel or battle, whether or not lost property or a fugitive will be found, the outcome of a long journey, or anything else that permits a binary yes/no answer. To operate the ‘Sphere’ in the case of a sick person, you take the first name of the patient and convert the letters of his or her name into their numerical equivalents – which are found next to or inside the ‘Sphere’. In the case of the first of two ‘Spheres’ found in Oxford, Bodleian Library, MS. Digby 46, a typical example of this device from a fourteenth-century fortune-telling miscellany (Figure 1), the letters and their numerical equivalents are found in the two outer bands of the diagram. The values of the letters are added up to make a total for the name. To this total, the number of the day of the moon on which the patient first fell sick, and usually the number of the planetary weekday, are added. The number for the day of the moon would be any value between one and thirty, and could be easily calculated by using lunar tables or an astrolabe, and the planetary weekdays and numerical equivalents are usually found listed within or next to the diagram – in this example, in sections of the outer band of the ‘Sphere’. This grand total of name, lunar day and planetary day is then divided by thirty (sometimes twenty-nine, but this tradition had petered out by the later middle ages as there were perceived to be thirty days of the moon). The remainder provides the answer: if it is located in the top half of the diagram, the patient will live, if in the bottom, the patient will die. The central hemispheres are usually arranged in three columns, indicating whether recovery or death would be in the short, medium or long term – in this example from MS. Digby 46, ‘parva’, ‘media’ or ‘magna vita’ or ‘mors’.
Mirfield's onomancy in his Breviarium, of course, does not work in exactly the same way as the ‘Sphere’. Possibly to make the method simpler for the semi-literate, he takes the value of the name of the sick person, and adds to it a new element – the value of the name of the messenger. To this total is added the number of the planetary weekday, and the outcome depends on whether the total is odd or even. This method means that the number of the day of the moon does not need to be calculated, there is no division involved and no remainder numbers to be memorized, so it can be committed to memory much more easily than a ‘Sphere’. Despite these differences, Mirfield's onomancy derives from the ‘Sphere of Life and Death’ or an earlier ancestor, although whether he actually composed this variation himself is not known.
The ‘Sphere’ is often called the ‘Sphere of Life and Death’ (‘Spera de Vita et Morte’) in manuscripts, but it also takes many other names which attribute it to various ancient and early Christian authorities, although it is highly unlikely that any of these authorities was responsible for the composition of this device. Pseudepigrapha are more than common in the middle ages, as the attribution of a respected authority was seen to add sophistication as well as proof of veracity or reliability to a text. The most common attribution of the ‘Sphere’ in the later middle ages is to Pythagoras, and it is not difficult to see why. Pythagoras (c.570–c.495 B.C.E.) was famously associated with number mysticism as well as medicine throughout the middle ages.  Another very common attribution is to Apuleius (c.125–c.180 C.E.), the second-century Roman author of the Golden Ass, a novel on magic and metamorphosis. While this work did not circulate widely in the Latin West between the sixth and fourteenth centuries, Apuleius had a reputation in the early middle ages as a magician due to his Apologia, a work written in self-defence against a charge of magic.  Apuleius had also been spuriously associated with a fairly popular medical herbal since late antiquity, which survives in at least sixty manuscripts from the sixth to the fifteenth centuries.  So Apuleius was associated with both the occult and medicine in the early middle ages. A third common acknowledgement is to Apollonius – although, as Chardonnens has shown, this is probably a corruption of Apuleius.  However, the attribution still makes sense. While there were many ancient authorities with this name, one of the most well known was Apollonius of Tyana (c.15–c.100 C.E.) – a Greek Neopythagorean philosopher, about whom we know very little, but who was thought, by his biographer Philostratus at least, to have predicted a plague by means of magic.  Furthermore, medieval Islamic scholars dubbed Apollonius the ‘Lord of the Talismans’ and spuriously credited him with having written several occult works.  There are further ascriptions to other ancient authorities, such as Petosiris, and early Christian authorities such as Crato (a Greek philosopher who converted to Christianity) and St. Donatus.
Sigerist postulates that the translation of the ‘Sphere’ from Greek into Latin probably took place in the sixth century, as ‘such translations were made in large numbers’ at this time,  and although this is pure speculation, most scholars have since agreed on this date. In any case, the first surviving Latin example that we have dates to 805 (Cologne, Erzbischöflichen Diözesan- und Dombibliothek, 83.II fo. 218v), and there are many more extant examples from the ninth to the eleventh centuries. However, an interesting problem occurred in the translation of the ‘Sphere’ from Greek into Latin. All Greek letters have corresponding numbers, but in Latin, only certain letters do, and not the commonest ones by any stretch of the imagination – C, D, I, L, M, V and X.  The results of this were fourfold. First, the number-letter correlations varied widely from device to device, as confusion over the values assigned to particular letters and errors in copying occurred. Second, multiple examples frequently appear close to each other in the same manuscript with different remainders. For example, Oxford, St. John's College, MS. 17, a very famous computistical manuscript dating from c.1110, has two examples of ‘Spheres’ copied next to each other on fo. 41r (Figure 2); but twenty-one is the remainder signifying ‘life’ in the upper (left) example, and signifying ‘death’ in the lower (right). Third, the same remainder might appear in both hemispheres of a single device, such as a second ‘Sphere’ in Oxford, Bodleian Library, MS. Digby 46 fo. 107v (Figure 3), which has eight as a remainder signifying both ‘life’ and ‘death’. Finally, certain remainders simply do not appear at all, such as in Cambridge, St. John's College, MS. 37 fo. 53v (Figure 4), a fifteenth-century medical miscellany, in which twenty is not present in either hemisphere.
Thus, if the ‘Sphere’ was corrupted – and obviously so in the minds of scribes who copied different devices together, perhaps trying to find the right version – then why did it survive? As Boudet points out, this corruption in fact paradoxically contributed to the device's endurance, since if it failed to predict the outcome accurately, this could be blamed not on the system, but on the version used.  And, as we shall see, the corruption and ambiguity that the ‘Sphere’ could produce might also be helpful to the late medieval physician, as he negotiated the tricky path between caring for the body and caring for the soul of his patient.
Once translated into Latin, the ‘Sphere’ was passed down to the later middle ages via the early medieval computistical miscellanies that flourished from the ninth to the eleventh centuries.  Computus, that is, the measurement of time with recourse to the heavens in order to calculate major Christian feasts such as Easter, has little in common with the ‘Sphere’, except an element of calculation and time-keeping. So it seems that the main reason for this companionship of ‘Spheres’ and computistical texts is largely an attraction between diagrams. The example of Oxford, St. John's College, MS. 17 (Figure 5) neatly shows how divinatory ‘Spheres’ became disguised as respectable computistical tables. On fo. 40v is a round computistical chart, and on the opposing recto fo. 41r are the two ‘Spheres’ we have just seen, which look totally in place within this manuscript, but are in fact illicit divinatory items. The ‘Sphere’ had cleverly disguised itself as a legitimate computistical table.  But while the earlier medieval instances – at least in English manuscripts – are found almost solely in a computistical context,  the examples dating from 1100 onwards are found in all kinds of manuscripts and with a dazzling array of travelling companions.
In the later middle ages, the ‘Sphere’ is located in a great number of manuscripts. This author has so far found examples in around 200 of European provenance from throughout the middle ages and beyond, sixty-two of which were produced in England between 1100 and 1500.  These manuscripts are extremely varied in content – from scientific miscellanies, to occult books, to those containing theological works; as well as a great variety of treatises on medicine, from books used by the educated physician to the commonplace books of householders. And, unlike the early medieval ‘Sphere’, very little scholarly work has been carried out on its late medieval counterpart, aside from two articles by Linda Ehrsam Voigts,  and a short section in a book by Benedek Láng, writing about eastern European manuscripts of ritual magic.  Other works make nothing much more than a passing reference to the late medieval ‘Sphere’.  This lack of scholarly attention renders the study and analysis of this extremely popular item even more pertinent.
Helpfully, several of the manuscripts in the late medieval English corpus can be confidently placed with particular owners. These owners neatly illustrate the range – both socio-cultural and geographic – of people who owned such a device in late medieval England. Cambridge, Trinity College, MS. O.1.57 belonged to an early fifteenth-century family of the lower gentry – the Haldenbys of Isham, Northamptonshire. A contents list in a contemporary hand tells us that this manuscript once contained a ‘Sphere’, which is now lost.  Another Trinity manuscript, MS. O.2.5, written in the early fourteenth century, has ‘Spheres’ on fos. 8r and 10r–11r. The second flyleaf contains a copy of a deed from ‘Robertus de Barry rector ecclesie de Begeley’, and then a sixteenth-century hand tells us that ‘Nomen totius huius libri Miscellanea Roberti de Barry quondam rector de Begeley qui vixit sub an. Dom. 1270’.  The de Barrys were an ancient aristocratic family of Irish and Welsh origin, whose notable members include Gerald of Wales (c.1146–c.1223). The family resided at Manorbier castle, Pembrokeshire, after the Norman conquest, and the family's estate included the manor of Begelly, where this Robert was rector. 
Several of the manuscripts – some of the earliest in the corpus written in the early twelfth century – can be placed in monastic ownership, thanks to their computistical context, which makes reference to specific saints' days. Oxford, St. John's College, MS. 17, written c.1110, was copied at Thorney abbey, Cambridgeshire; Los Angeles, J. Paul Getty Museum, MS. Ludwig XII.5 was possibly made at Worcester abbey at around the same time; and Cambridge, Trinity College, MS. O.7.41 was produced at Colchester Abbey c.1120. Two of these early twelfth-century manuscripts can be placed at Peterborough abbey: British Library, Cotton MS. Tiberius C I and British Library, Harleian MS. 3667.
Some later medieval manuscripts were also copied in and/or owned by monasteries. Cambridge, Trinity College, MS. O.2.45/British Library, Egerton MS. 843, both of which contain ‘Spheres’ and were once a whole manuscript, can be placed at Cerne abbey, Dorset, in the second half of the thirteenth century.  Additionally, a now-missing manuscript which contained a ‘Sphere’, which we know about thanks to a catalogue made by the Austin Friars of York in the fifteenth century, belonged to John Erghome, canon and regent master of York in the second half of the fourteenth century. Erghome bequeathed this manuscript to the Austin Friars, who possessed it in the fifteenth century.  Finally, the first of three sections of British Library, Royal MS. 12 G IV, written in the fourteenth and early fifteenth centuries, can be placed in the hands of John of Greenborough, infirmarer of St. Mary's priory, Coventry, due to a revealing colophon (fo. 187v), which will be discussed in more depth. Just from these few examples, then, we can see that ‘Spheres’ were owned by aristocracy and gentry, monks, abbeys and medical practitioners from Dorset to west Wales, the Midlands, East Anglia and York. But it is to the medical context of the ‘Sphere’ that this article will turn, in order to try to cast some light on why an item so condemned in canon law, and so completely devoid of any Hippocratic-Galenic medical theory, was copied and used by learned medical practitioners in the British Isles throughout the later middle ages.
The ‘Sphere’, of course, was by no means the only way of predicting the future in late medieval England – far from it. Techniques for predicting the future ranged from sophisticated, learned methods such as judicial astrology and complex forms of divination such as geomancy, chiromancy and scapulimancy,  to those used mainly by the learned physician, such as the Hippocratic-Galenic Signs of Death, sphygmology (pulse-reading) and uroscopy. Further down the scale were simple prognostics based on the lunar cycle, such as lunaries (moon books) and the propitious and non-propitious days for performing activities such as blood-letting. There were also magic rituals and experiments in the so-called ‘common tradition’ of magic to predict the outcomes of certain situations. But this article aims to show that the ‘Sphere’ is an item worthy of focused analysis, partly because of its ambiguous status between licit and illicit.
Simply put, it was not licit in the eyes of the church to practise divination, and there were three main objections: it usurped divine providence – the idea that only God can know the future; it went against the idea of man's free will; and, from late antiquity, it was perceived to operate with the express involvement of demons. Many theologians and canonists since the early Christian fathers had written condemnations of divination. Among the general condemnations, the most significant are book II of Augustine's On Christian Doctrine (397) and his City of God (before 417); Isidore of Seville's (d. 636) Etymologiae; John of Salisbury's Policraticus (c.1159); and Thomas Aquinas's Summa Theologiae (1265–74). None of these works condemns the ‘Sphere’ explicitly, though John of Salisbury does vaguely refer to ‘tables which are called Pythagorean’ in his condemnation of superstitious practices,  but all four writers make it very clear that divination in general is an illegal practice. 
The Decretum, or to give it its original name, Concordia Discordantium Canonum, composed sometime in the eleven-forties at Bologna, is a vast corpus of canon law collected together by Gratian, a lawyer-monk. In condemning superstitious practices of all kinds, this work does specifically mention the ‘Sphere’, ‘sive per quosdam numeros litterarum, et lunae, per Pitagoricam nigromantiam egrotantium vitam vel mortem, vel prospera vel adversa futura inquirunt’.  This is not the vague ‘Pythagorean tables’ of John of Salisbury but rather definite censure of the ‘Sphere’. Gratian was collecting canons from a vast array of sources, and it is not clear from where this section of the work was copied, or when it was written, but it seems likely that the condemnation of the ‘Sphere’, at least, cannot have been written much before Gratian's own time, the clue being the use of the word ‘nigromantia’. In its original, ancient Greek meaning, this word literally meant ‘divination by the dead’ (nekros = ‘dead’ and manteia = ‘divination’), and Isidore of Seville had, in the seventh century, given it its original definition in his Etymologiae. However, by the later middle ages, this term had come to mean something quite different. ‘Necro’ had become confused with ‘nigro’ – coming from ‘niger’, the Latin for black. ‘Nigromantia’ became the translation for the Arabic word for magic ‘sihr’, and so ‘necromantia’ or ‘nigromantia’ was often used in a vague sense to define illicit magical practices. The earliest known attestation of this new meaning of necromancy is in Petrus Diaconus's biography of Constantine the African, the eleventh-century translator of Arabic medical texts into Latin, written sometime in the eleven-thirties.  The use of the word ‘nigromantia’ in Gratian is the later definition – in this case it seems to be describing a general sort of impermissible magic – and so we can safely say that this condemnation was probably not written before the start of the twelfth century, and may even have been written in Gratian's own time. 
Gratian's influence across the Latin West cannot be overstated,  and so it is not surprising to find his condemnation of the ‘Sphere’ copied verbatim into several pastoral manuals that circulated in England in the later middle ages. These manuals were intended for use by priests to work out the penance to be administered for particular sins which had been admitted during confession. The earliest of these was Thomas of Chobham's extremely popular Summa Confessorum (finished by 1216).  The second of which this author is aware is the aforementioned Florarium Bartholomei of John Mirfield, produced at the turn of the fifteenth century.  Finally, this condemnation is paraphrased in Middle English in the late medieval vernacular self-help treatise Diues and Pauper (c.1405–10), probably intended for well-to-do families as a guide to living a virtuous life. Diues and Pauper lays out sins and punishments arranged by the Ten Commandments. Under the First Commandment, chapter thirty-four gives a lengthy list of condemned superstitious practices, including ‘dyvynyn of mannys lyf or deth be numbrys and be þe sper of Pittagoras’.  This is an even more definite reference to the ‘Sphere’ than the condemnation in Latin on which it is based, since it refers to the device by one of its common names – the ‘Sphere of Pythagoras’.
So, canon law, in theory, said that it was illicit to use a ‘Sphere’. But, in practice, was anybody actually prosecuted for using such a device? This author has yet to uncover any evidence from the middle ages of someone being reprimanded for using this item specifically, but the rare court records that survive from the period show that people in medieval England were occasionally punished – though usually not severely – for engaging in divinatory practices and claiming to predict life or death.  The only evidence of prosecution for the use of a ‘Sphere’ is from 1564, when John Betson, a clergyman, was ordered by the northern court of high commission to hand in his copies of ‘Plato's Sphere’ and ‘Pythagoras's Sphere’, which he had used to recover stolen goods, before doing public penance by declaration in the markets of Yarm, Richmond and Northallerton.  Looking at the evidence from medieval trials for divination and the case of Betson, then, it is likely that if a prosecution for using a ‘Sphere’ did take place pre-1500, then the punishment would not have been particularly severe, ranging from the handing over of the device to the authorities to performing public penance.
The use of a ‘Sphere of Life and Death’, then, was not permissible in the eyes of the church. But it seems that this law was not followed, because, as we have seen, its manuscript context reveals that such a device appealed to all sorts of people, including the university-trained physician. We know that many of the people who used the ‘Sphere’ were aware of its corruptions, because multiple redactions were often copied together, seemingly with the intention of locating the right version. Therefore, on first impression, it might appear strange that the ‘Sphere’ was an item which appealed to the learned, university-trained physician. But on further examination, several reasons emerge as to why such a device could and did hold interest for such a professional.
Turning to the manuscript evidence, the ‘Sphere’ appears in the same hand as tracts of learned Hippocratic-Galenic medicine, as well as, in several instances, treatises on the curriculum of the medical faculty at Oxford and Cambridge universities, and universities further afield. The only firm evidence of an Oxbridge-trained physician possessing manuscripts containing ‘Spheres’ relates to Roger Marchall (d. 1477), trained in medicine at Peterhouse College, Cambridge, and later physician to Edward IV. Marchall, then, was a medical practitioner of the highest rank. His distinctive hand means that several manuscripts can be traced to his ownership, as he made selective contents lists of those he acquired, which indicate the precise items in which he was interested within them. Three manuscripts of the corpus can be placed in Marchall's ownership: British Library, Harleian MS. 267, British Library, Harleian MS. 531 and Cambridge, MS. Peterhouse 222. While Marchall leaves the ‘Spheres’ in Harleian MS. 267 and MS. Peterhouse 222 out of his contents lists, he includes ‘Spera Pictagore cum usu et opere’ in his contents list of Harleian 531 – although sadly this ‘Sphere’ is no longer extant.  So Marchall took an active interest in the ‘Sphere’, as he included it in one of his contents lists, and this is striking evidence that one of the most important physicians in England of his time, who attended the king, owned and perhaps used the ‘Sphere’.
Other ‘Spheres’, too, can be placed firmly in the context of learned medicine, for example British Library, Sloane MS. 3229, a fifteenth-century manuscript of the Regimen Sanitatis Salernitanum. Written in the same hand throughout, it incorporates a ‘Sphere’ into the main body of the work at fos. 6v–7v. This work on regimen, organized by the six non-naturals (air; food and drink; sleep and waking; motion and rest; excretions and retentions; and dreams and passions of the soul) was based firmly in Galenic medicine, held in high regard as a scholarly medical text until the end of the middle ages and beyond, and was, of course, associated with the School of Salerno, thought to be the first medical university in the Latin West.  This text was therefore firmly in the realm of the learned physician. The most interesting facet of the inclusion of the ‘Sphere’ in this manuscript is the fact that it is not tacked on at the beginning or end, on a flyleaf or blank page, but rather incorporated into the work itself. A comparison with the critical edition of two related manuscripts  shows that, in the second part of the work, a section on winds, De Ventis, is followed immediately by that on diet, De Comodo Bone Diete, but in Sloane MS. 3229, the verses on winds end at the bottom of fo. 6r, and overleaf the scribe has decided to copy in a circular wind diagram (fo. 6v), followed by the ‘Sphere’ instructions in verse; and overleaf again (fo. 7r) is the ‘Sphere’ diagram, with the numbers corresponding to the planetary weekdays set out below, going over onto fo. 7v (see Figure 6). This is followed immediately by a further onomantic technique to determine the winner in a duel, before picking up again with the Regimen text, De Comodo Bone Diete. The rubricator of the manuscript later added the part of the work to which each folio pertained at the top of each page, but resisted doing so for fos. 6v–7r, perhaps in acknowledgement that the ‘Sphere’ was not a recognized part of the main Regimen.
As well as being incorporated into this work of regimen, ‘Spheres’ are also found with Nicholas of Salerno's (fl. 1150) Antidotarium. There can be no doubt that this work was on the curriculum of the faculty of medicine at Oxford University in the fourteenth century, as it is included in the Chancellor's and Proctor's Book of the university, written sometime before 1350, which set out the standard texts that medical students were expected to know and be able to lecture on.  ‘Spheres’ appear in the same hand as this work in two fifteenth-century manuscripts: Oxford, Bodleian Library, MS. Digby 29 has a ‘Sphere’ (fos. 193r–194r) and Nicholas's work (fo. 244r); and Cambridge, Trinity College, MS. O.9.10 has an Anglo-Norman ‘Sphere’ (fo. 75v) and the Antidotarium (fo. 27r). The ‘Sphere’ also appears with Giles of Corbeil's extremely popular poem on uroscopy, De Urinis, which was often included in the Articella – the corpus of medical texts that university-trained students were expected to know. MS. Digby 29 contains Giles's poem (fo. 76v) and the ‘Sphere’ (fos. 193r–194r); and the fourteenth-century British Library, Sloane MS. 521 contains De Urinis (fo. 25r) and the ‘Sphere’ (fo. 45r–v). There is also a ‘Sphere’ in British Library, Harleian MS. 5311 leaf J (Figure 7),  a physician's almanac designed to be worn on the belt, which is beautifully illuminated and contains a wealth of material of interest to the learned doctor – uroscopy diagrams, a zodiac man and lunar tables. This was probably as much an item to be worn to give status to the physician as it was useful – as Jones points out, it was probably there mainly to reassure the patient of the doctor's capabilities.  It is likely that the (mainly basic) information within it was committed to memory by the physician, but its luxurious nature and ease of display on the belt give the impression that it was designed for an upmarket, learned practitioner.
As well as this undeniable appeal to the learned physician, the ‘Sphere’ was also of interest to medical practitioners slightly lower down the scale – those who were literate, but not university trained – hence its appearance in the thirteenth- and fourteenth-century manuscript British Library, Royal MS. 12 G IV fo. 160r (Figure 8), along with Gilbert the Englishman's Compendium Medicinae – a treatise which made theoretical medicine easy for the non-university-trained physician.  As we have seen, this manuscript was owned and presumably used by John of Greenborough, infirmarer of St. Mary's abbey, Coventry. While this manuscript was compiled in three different stages across two centuries, and the ‘Sphere’ is in a later hand than Gilbert's work, we know that it all travelled together at the same time due to the revealing colophon at the end of the work on fo. 187v (Figure 9), written in the same hand as the ‘Sphere’:
Frater Iohannes de Grenborough per xxx annos et plus nuper infirmarius emebat istum librum vocatum Gilbertinum ad utilitatem infirmorum in ecclesia Couentre existentium, et ea que in nouis quaternis sunt scripta compilauit a practicis phisicorum Anglie Hibernie Iudeorum Saracenorum Lumbardorum et Salernita[no]rum et expendebat multa in medicis circa compilationem illarum medicinarum. Multa in nouis quaternis suprascripta per practicam sunt vera, set plures phisici nolunt approbare ea, quia multi illorum ignorant practicam sed multa verba et vacua in ventum seminant. 
Why would this device appeal to the university-trained and literate practitioner, as the manuscript evidence suggests, since it was corrupted, and very simple to use? There are in fact several possible reasons for its popularity among medical elites. First, the ‘Sphere’ makes use of a lunar and planetary element that was perfectly in line with mainstream medical principles. It is well known that the macrocosm of the universe was thought to have an effect on the microcosm – in this case, the human body. Texts on the Egyptian days – the twenty-four days of the year that were considered to be especially unlucky for all enterprises, including medicine – are popular in medieval manuscripts,  as are more specifically medically oriented texts, such as those outlining the days of the moon considered good or bad for activities such as bloodletting. Hippocratic and Galenic medicine spoke of the ‘critical days’ of acute illnesses, that is, when the physician could expect a crisis in the patient's health.  And, of course, in the later middle ages there existed a complex, sophisticated medical astrology which was the domain of the learned physician, who drew up nativities and elections to make all kinds of prognostications regarding the health of his patients.  While the astrological elements of the ‘Sphere’ are very basic, the intellectual link between this device and more complex astrology was nevertheless present. The inclusion of this lunar and planetary element in the ‘Sphere’, then, associated it with learned medicine, even if its onomantic component did not.
Second, we must acknowledge that of all the methods of prognosis available to the learned physician – from the Hippocratic and Galenic art of observing the patient carefully to produce a prognosis, to uroscopy and sphygmology, other divinatory methods and complex astrology – the ‘Sphere’ was probably one of the quickest ways of obtaining a definite answer. The Signs of Death of Hippocratic-Galenic medicine depended strongly on the doctor having good knowledge of his patient's usual demeanour; uroscopy could only be done once the patient had produced urine and even then, making a prognostication was an interpretative ‘art’ rather than an exact ‘science’. Other forms of divination like geomancy were tricky and required a good deal of skill and training – the very fact that professional geomancers existed is testament to this  – and astrology could also take years to master correctly, and was open to interpretation. The ‘Sphere’ was also much quicker to use than many other prognostics. For example, the anonymous thirteenth-century pulse-reading tract Summa Pulsuum gives instructions on predicting death with recourse to the pulse:
The hour of death can be foretold by the failing pulse on a critical day, and the hour of convalescence by a rising one. Suppose, for example, that the patient has a failing pulse; whether he will die or not from this sickness is determined thus. You must reckon from the first failure of his pulse to the second, [finding] the time of day when it happens and the number of beats between the two – say you find thirty beats between the first and second failures at the third hour of the day. But since it is improper for you to stay there in continual calculation, come back the next day at the same hour and count the beats of his pulse again. The first day you counted thirty beats between one failure of the pulse and the next; if now the failure comes on the fifteenth beat, so that you have fifteen strong beats where before you had thirty, it is a sign that when the same number of hours have passed once more, having lost [a further] fifteen beats, the patient will die at that moment. You should treat a rising pulse in the same manner … 
Therefore it could take up to two days to work out when the patient might die, so if s/he was already critically ill, there was a chance that the patient would die before an answer could be reached. In contrast, the ‘Sphere’ could produce an answer in under a minute – and it offered a definite answer seemingly not open to interpretation. The patient would live or die, quickly or slowly.
However, while the ‘Sphere’ claimed to offer a definite answer, as we have seen, its corruptions and ambiguities meant that sometimes it did not. Ambiguity was often a very useful tool for the learned physician, because the prediction of death was a very tricky area. On the one hand, it was important to keep the patient's spirits high at all times even if the case looked hopeless, but it was also vital that a patient did not die without confessing his sins to a priest and receiving the last rites. In his Breviarium, Mirfield explains why a doctor must never tell a patient that he might die:
[The physician should] permit his patients to indulge themselves in whatever is pleasing to them (provided that this be not prejudicial to his treatment), and by means of blandishments, and of pleasant and soothing speeches, he should comfort his patient, and on every occasion should promise him restoration to health, even if the physician himself shall regard the case as desperate; for by means of such heartening words the sick man is imbued with a courage which strengthens his constitution and fortifies it to resist the disease; so that from Nature herself there proceeds a reaction which is more efficacious than that produced by the physician with his instruments and medicines. Let the physician, however, acquaint the friends of his patients with the truth, and discuss the case fully with them as he shall deem best, lest he incur scandal or loss of reputation from inability to proffer a satisfactory statement of the case, and lest the friends of the patient regard him with distrust: nor will he be held responsible for having caused the death of the patient who shall die; but he will be given credit for having cured the man who lives and is restored to health. 
Mirfield here is copying almost verbatim from the introduction of William of Saliceto's (fl. c.1275) Cyrugia, which was itself copied in part from the Visit of the Physician to the Patient of Archimatthaeus the Salernitan (fl. 1100). Therefore, Mirfield was echoing a widely held view among medieval medical practitioners: a doctor must never tell a patient that s/he will die, but instead, to avoid any censure, warn the patient's family that death is likely. Canon twenty-two of the Fourth Lateran Council held in 1215 also states that a patient's spirits should be kept high, decreeing that all patients should confess before receiving medical treatment, because the sight of a priest alone could make a patient lose hope and therefore the will to live. This way, no one patient felt singled out:
when physicians of the body are called to the bedside of the sick, before all else they admonish them to call for the physician of souls, so that after spiritual health has been restored to them, the application of bodily medicine may be of greater benefit, for the cause being removed the effect will pass away. We publish this decree for the reason that some, when they are sick and are advised by the physician in the course of the sickness to attend to the salvation of their soul, give up all hope and yield more easily to the danger of death. 
Medical and theological authorities, then, agreed that the patient's hopes must be kept high at all times. But at the same time a physician could not risk the patient dying without receiving the last rites. So sometimes the ambiguity raised by using a device such as a ‘Sphere’ was a good thing, as it could help the physician to extract himself from a hard-to-call case with his reputation intact, and without lying.
John Mirfield's inclusion of a ‘Sphere'-like prognostic in his medical manual, and his condemnation of the ‘Sphere’ in his pastoral work, perfectly illustrates the ambiguous status of this device in later medieval England. It was, on the one hand, an item of illicit divination that was specifically condemned in canon law and pastoral manuals, referred to even as ‘necromancy’ in Gratian's Decretum, which linked it to much more sinister black magic. At the same time, the ‘Sphere’ was a useful medical tool, associated with licit computistical tables and medical astrology, which could be used quickly and in the absence of the patient if necessary. It also contained some corruptions from its translation into Latin which could have made it even more useful to the learned physician as he cared for his patients. The ‘Sphere of Life and Death’, then, was partly licit medicine, and partly illicit divination, and shows that a more nuanced approach to categorization must be taken when dealing with such ambiguous items.