Who was Taliesin?
(1) The Historical Poet
This view of Taliesin sees him as the bard of the Brythonic chieftain Urien in the sixth century kingdom of Rheged which extended from Strathclyde (around modern Glasgow) down into Cumbria in the northern part of the Lake District. Of the mass of poems in The Book of Taliesin a few are still held to be possibly written by this poet. They mainly sing the praises of his lord in common with much of the poetry composed by tribal bards at this time. But The Book of Taliesin is a fourteenth century manuscript collection given that name when discovered in a library in the seventeenth century. So the poems in it are not, in the form we have them, from the sixth century but later copies. As, initially, no-one could read them, they were assumed to be the work of a poet writing in Old Welsh. By now it has been established that most of the poems must be much more recent than that and all are, in fact, written in Middle Welsh in the manuscript versions we have.
If that was all that could be said, Taliesin would be no better known than Aneirin, another poet from what is now southern Scotland writing around the same time, who composed a series of elegies for the members of the Gododdin tribe who were wiped out in an attack on the Angles at the battle of Catraeth (modern Catterick in Yorkshire). That is, as with Aneirin, the debate about him would mainly be restricted to scholars attempting to date the poems from linguistic and historical evidence or discussing their contribution to the successive literary tradition in Welsh.
But Taliesin, like Myrddin, a third poet identified with the same area, has been mythologised in a number of ways. And if the mythologisation of Myrddin as Merlin is at least clear and transparent, Taliesin has been transformed into a much more complex wizard for later generations.
(2) The Legendary Bard
It is disputed how many, if any, of the poems in The Book of Taliesin, the thirteenth century manuscript that collects poems attributed to him, are actually by the sixth century bard mentioned by Nennius in the Historia Brittonum. It is known that some of them are by medieval bards donning the persona of Taliesin. The nature of the AWEN is mentioned in several of the poems and it is clear that there was an ongoing debate about the source of the AWEN between these bards. See the Medieval Welsh Bards page for examples from identified poets. Here are a few examples :
Armes Prydein (The Prophecies of Britain) begins with the phrase 'Dygogan Awen ...' (Awen foretells ...).
The poem 'Mydwyd Merweryd' or 'Kadeir Taliesin', contains the question "Where does Awen flow to / at midnight and midday?" Later in the poem the flow of inspirations is referrd to as 'Gwion's river'; (in the later prose Tale of Taliesin , Gwion tastes the drops from Cerridwen's cauldron and is eventually transformed into Taliesin).
In the poem 'Golychaf - i Gulwyd' he claims to have sung before Brochfael of Powys "who loved my awen" or possibly "whom my awen delighted in".
The poem 'Kadeir Teyrnon' opens with the declaration that the poem is "brilliant ... and of immeasurable awen".
Later in the same poem there is an extended conceit suggesting that AWEN can be divided up into three "ogyrwen" and apparently linking this to the Trinity using word play that deliberately confuses the word for 'cauldron' with that for 'sovereign' (or deity). This is an example of the poem's advertised brilliance.
Many of the poems in The Book of Taliesin contain prophecies which link them to historical events in the ninth and tenth centuries. Others refer to stories that link them with prose tales in Y Mabinogi. Or with legendary exploits such as the raid by Arthur on Annwfn – the Brythonic Other World – to capture a magical cauldron. What is clear from consideration of the range of poems attributed to Taliesin is that, like Arthur, his name became a magnet for disparate material but also that he became the ‘type’ of the inspired poet. When later generations of Welsh poets in the Middle Ages looked back to the sources of their tradition, the place of beginning was ‘The Old North’, an area of southern Scotland and Northern England. Here the earliest poets using Welsh after it had developed from the Brythonic language some time after the Roman occupation, were seen as forefathers of the Welsh bardic tradition – one was called ‘Tad Awen’ (Father of the Muse) by Nennius in the 9th century, though none of his poems have survived. Collectively they were called the ‘Cynfeirdd’ (the earliest poets) and Taliesin became their iconic representative. So already, by the ninth century, he was being represented as a prophet and a magical figure who was present (whether imaginatively or otherwise) at various historical and legendary events from the beginning of the world to Arthur’s raid on the Other World. He was, in the Second Branch of Y Mabinogi, one of the seven who returned with the head of Brân from Ireland and sojourned with that head in Gwales in a timeless suspension of the everyday world. This is the poet as ‘awenydd’, an inspired individual such as those described by Gerald of Wales in the twelfth century, going into a prophetic or visionary state. He could now be regarded as the Spirit of Poetry.
(3) The Spirit of Poetry
At some point, inevitably, Taliesin entered the folklore tradition. The familiar story about Gwion Bach being given the job of stirring the cauldron of the witch Ceridwen and gaining universal knowledge by tasting a drop of the contents using a common folklore narrative pattern. Similarly the sequence of shape-shifting as Ceridwen chases him and each turn into something different until she, as a hen, gobbles him up when he is disguised as a seed. His rebirth from her womb, his survival in his new identity as Taliesin, and his subsequent exploits at the court of Maelgwn Gwynedd, link this story to the legend of the gifted poet. In one sense this is just another example of the ‘magnet’ effect mentioned above, with the name Taliesin simply being attached to existing folk tale motifs. But in another sense it indicates how the figurative shape-shifter has become a ‘type’ not just of the Welsh bardic tradition but of the Spirit of Poetry itself.
Patrick Ford in his discussion of Ystoria Taliesin (the sixteenth century prose tale in Welsh based on his continued presence on the folk tradition) says this:
“Clearly the tales of Gwion Bach and Taliesin cannot be lightly dismissed as “folktale” or late developments. Perceptible in them and in their attendant poems, despite the layering of successive generations and external influences, lies the myth of the primeval poet, in whom resides all wisdom.” 
Patrick Ford sees the story of Gwion being swallowed by Ceridwen and cast into the waters in a leathern bag to emerge as Taliesin as a death and rebirth theme, still being retold in the version known as Ystoria Taliesin. He presents this as the poet sacrificing himself to his muse, to be compared therefore with mythological figures such as Odin sacrificing himself to himself, and with representations of the Spirit of Poetry in Irish stories such as the one discussed HERE. He defines the ideal form of the awenydd or inspired poet and the condition that such a figure aspires to attain.
Many of the elements in the folktale can be found in the poems of The Book of Taliesin. For instance, in a number of the poems the source of poetry is identified as a cauldron, most often identified as the Cauldron of Ceridwen. But in one poem there is a quite dense poetic construction in which the word for cauldron (peir) can also mean ‘sovereign’ which is often used as a metonym for God. So the words
“pan doeth o peir / ogyrwen awen teir” can be translated
“when there came from the cauldron / the ogyrwen of three-fold inspiration”,
or they could equally be translated as
“when there came from the Sovereign (God) / the three aspects of inspiration”.
In the most recent scholarly edition of these poems Marged Haycock describes this as “a nicely calculated ambiguity”, indicating that both meanings are intended here. The Book of Taliesin is a difficult text to interpret even for scholars and the poem from which these lines come – Kadeir Teÿrnon – has been described as bewildering and unintelligible. So any interpretations are provisional. But from its use here and elsewhere it is clear that ‘ogyrwen’ is the name of at least one of the three divisions of awen, or it is a term describing all three ( so, ‘the three ogyrwen of awen’). But what is clear is that the poem deliberately conflates the cauldron and God (as the Trinity) as its source. We might regard this as a neat bit of theology or an example of clever bardic word-wizardry of the sort the Taliesin figure often boasts about.
This reference is, in fact, just one example of a debate about the nature of awen among the early Welsh bards. In a discussion of this issue Patrick Ford cites an exchange between the bards Rhys Goch and Llywelyn ap Moel about the source of awen as to whether is comes from the “Holy Spirit” or from “The Cauldron of Ceridwen” and also cites a line from another medieval Welsh bard, called Prydydd y Moch, who conflates the two options with the line “The Lord God gives me sweet awen , as from the cauldron of Ceridwen”. It is thought that Prydydd y Moch might have written some of the poems in The Book of Taliesin and so would be Taliesin himself in his thirteenth century guise. That is, he would have adopted the Taliesin persona for the purposes of an awenydd rather than in the context of his duties as a court poet for which he would use either his own name or his recognised bardic title (Llywarch ap Llewelyn/Prydydd y Moch ).
Patrick Ford comments; “It seems appropriate that the persona of Taliesin, as representative of the old native tradition, should insist on the magical origins of awen and its use as a vehicle for traditional kinds of knowledge.”  But he also refers to the view of Marged Haycock that the medieval Welsh bards were also working within the context of Christianity and the persona of Taliesin also had to function within this world view rather than as a “druid desperately making a last stand for paganism”. He looked both ways, expressing current Christian thinking about God conceived of as a Trinity, locking this into the concept of the threefold nature of awen, but also maintaining his status as one who had links back to the older world.
So Taliesin denounces the other bards not as Gildas had done for their ungodliness, but because they have lost touch with the real roots of poetry, with the authentic awen. At the same time he ensures that he cannot himself be accused of being ungodly. But alongside this older notion awen is a developing concept during the Middle Ages and its divine nature necessarily takes on the prevalent Christian sense of divinity.
By the end of the eighteenth century, when Iolo Morganwg was putting together the scattered remnants of this tradition and the process of re-interpreting it was getting under way, the awen became the central symbol and ideal expression of the druidic renaissance as it is still held to be today both in the religious practice of druidry and in the continuing bardic tradition among Welsh language poets.
 Patrick Ford Ystoria Taliesin (Cardiff, 1992)
 Marged Haycock Legendary Poems from the Book of Taliesin (CMCS, 2007).
 Patrick Ford’s introduction to his edition of Y Mabinogi and Other Medieval Welsh Tales (1977) which contains the story of Gwion Bach and Taliesin.
 ‘Preiddeu Annwn and the Figure of Taliesin’ in Studia Celtica18/19, as cited by Ford, though since this article was published Marged Haycock has developed her ideas in greater detail in the work cited at  above and in also her more recent Prophetic Poems from the Book of Taliesin (2013).