Putter summarises the known facts about the authorship of the poems in the Nero A.x manuscript:

The end of the fourteenth century and the dialect are certainly reasonable inferences derived from the Nero A.x manuscript.  It also seems very reasonable to infer that the poet was an Englishman (the dialect in Nero A.x is certainly convincingly idiomatic,) but where is the evidence that the poet wrote somewhere in England?  The problem is that there is absolutely no evidence external to Nero A.x pointing to the identity of the Gawain-Poet.

The Nero A.x manuscript itself, in the British Library, contains only the four poems commonly referred to as Pearl, Cleanness, Patience, and Sir Gawain and the Green Knight.  The manuscript is thought to be a copy, but there is some evidence in the foliation that the poems have always been bound together in this order.  The manuscript has been dated on somewhat slender grounds to about 1400,^[1] and the scribe has been localised as coming from the region of south east Cheshire, south west Derbyshire and north west Staffordshire [MCINTOSH86], an area centred roughly around Holmes Chapel in Cheshire to Leek in Staffordshire.  Internal evidence suggests strongly that the poems were composed no earlier than the closing decades of the fourteenth century, and a date of around 1390 is perhaps most generally accepted. The poems were first published in the nineteenth century [MADDEN39] [MORRIS69] and have since been recognised as of great literary merit.  Despite their significance, the authorship of this work remains in very considerable doubt, and most would agree that the only acceptable name for the Gawain-Poet to date is “anonymous”.  As far as dating and location are concerned, all we can say is that the manuscript was prepared by a scribe whose style was that of the Leek area somewhere around 1400.  It is, however, perfectly clear from the text that the native dialect of the author was that of the north west, with considerable influence from Old Norse.  Dating estimates cannot be precise, and error limits of ±10 years are probably the most optimistic we can apply.

It is almost generally accepted on literary grounds that a single poet was responsible for all the poems, but there is no hard evidence for this.  A large part of the evidence for authorship presented in this work comes from the poem Sir Gawain and the Green Knight, but we have not hesitated to draw on evidence from the other poems, particularly Pearl, when this seems appropriate.  Although we concur with the general opinion that a single poet produced all the poems in the Nero A.x manuscript, we are confident that withdrawing evidence from the other poems does not weaken the argument for attribution unduly.  Indeed, one could reverse the argument and use evidence from the other poems to increase confidence in common authorship.

There have been many earlier efforts to identify the Gawain-Poet but we must confess to a strong disposition to agree wholeheartedly with Pearsall and Putter that

and

In any attempt to identify the Gawain-Poet it is important to distinguish between direct and circumstantial evidence.  In the absence of any documentary evidence external to the Nero A.x manuscript, it has generally been assumed that any evidence derived from the content of the manuscript can be thought of as direct evidence.  For example, Greenwood [GREENWOOD56] and Kooper [KOOPER82] noted that line 106 in the published editions of Sir Gawain and the Green Knight is line 101 in the manuscript (the “bob” lines are written in the right margin rather than occupying a line by themselves,) and that the roman numeral ci represents the arabic 101.  This line contains the word mas and hence the name of the Gawain-Poet can be identified with Masci, the name of a prominent Cheshire family at that time.  Following up on this name, Vantuono [VANTUONO75] [VANTUONO81] claimed to recognise the name J. Mascy in marginal material of Sir Gawain and the Green Knight (folio 114) and beneath an illuminated letter in Cleanness (folio 62v), and the name Macy at the bottom of a folio in Sir Gawain and the Green Knight (but see the comment of Putter above).  Next it is important to identify the name with an historical character.  There is documentary evidence that a John de Mascy was rector of Ashton on Mersey from 1364 to 1401.  A John de Mascy of Sale (presumably the same man;  the church at Ashton on Mersey is little more than a half a mile from the centre of Sale) is recorded as a priest and a civil servant between 1377 and 1389.  So it was proposed that a member of the Mascy family of Cheshire (and probably John) was the Gawain-Poet.  Finally we need to compare aspects of the candidate's life with the subject matter of the Nero A.x manuscript.  Any correspondences we find constitute useful circumstantial evidence supporting the identification of the Gawain-Poet.  This leads us to a distinction between the differing qualities of circumstantial evidences:  those for which we have direct evidence, and those which we might infer as possible or probable.  Thus we might infer from his position as priest that it was perhaps even probable that John de Mascy was both literate and familiar with the Vulgate bible, although many local priests at that time had only a very minimal education.  We might also infer it was at least possible that he might have been familiar with the ritualistic detail of the hunt through his possible connections with local nobility.  Such inferences must carry far less weight than if we could produce (which we can't) documentary evidence that Mascy was a university graduate and had been appointed as chief huntsman to some local noble.  If we might misquote T. S. Eliot out of context, it is the difference between what might have been and what has been.

The identification process thus starts from an element of direct evidence for a name in the text, and we next proceed to an identification of the name with an historical person (an imaginative jump.)  Finally we support the identification by linking passages in the Nero A.x manuscript to events or experiences in the life of the historical person for which we should have direct evidence - for a poet can only write about happenings within his own experience.

It is this linking process which can provide good, convincing circumstantial evidence (but not direct evidence) for an identification of an historical person with the Gawain-Poet.  We should be clear that although we require direct evidence (i.e. external to Nero A.x manuscript) about the life of a candidate, the link to the poems is still only circumstantial evidence.  Ideally of course the evidence and the life of the historical person should also lead us to new locations to search for new direct evidence.

We follow this procedure and first find a name embedded in the text, and then identify this name with an historically documented person.  We then compare events and experiences in the life of this candidate with the subject matter of the poems.  When we find a correspondence between his life and the Nero A.x manuscript we are faced with the decision between a coincidence and a significant parallel.  We can only build upon an accumulation of these correspondences to achieve confidence.  A single coincidence might be a chance occurrence and carries little weight, but two related coincidences are a surprise.  When we encounter three coincidences we start to think more seriously that these are not coincidences or chance events at all, and when we encounter many multiple coincidences we are sure we see design behind them.  It is on this basis that we proceed to an identification of the Gawain-Poet.  A more formal presentation of the procedure is given in Appendix A.

All quotations from the poems of the Nero A.x manuscript are taken from the edition published by Andrew and Waldron in 2002 [ANDREW02].