Was the medieval Christmas primarily a religious feast? Or a boisterous folk-festival? The answer is probably both!
The roots of the celebration of Christmas are probably too complicated to untangle. What we know, however, is that the celebration of this major church feast was established early on. A number of celebratory sermons from the 4th century are perfect witnesses to this, as are the contours of a formal liturgy from the 6th century and onwards. In general, though the exact date has been widely debated.
What we know is that In AD 336 the celebration of the Birth of Christ was listed on the 25th of December and figuring as the beginning of a Roman calendar, indicating that this was also intended to be considered the beginning of the church-year.
The first sermons preserved indicate that the 25th of December was chosen because of its affinity to winter-solstice. As Augustine wrote: “Hence it is that He was born on the day which is the shortest in our earthly reckoning and from which subsequent days begin to increase in length. He, therefore, who bent low and lifted us up chose the shortest day, yet the one whence light begins to increase.” 
But behind this date-picking was probably also a couple of other considerations. One was – perhaps – the wish to collapse the “new” Christmas feast with that of several traditional feasts, the Saturnalia and the Kalends, both regarded as a times occasioning boisterous popular feasting and giftgiving. Especially the birth of Sol Invictus, held since the end of the 3rd century was ritually superseded. This feast was intended to celebrate the rebirth of the sun and light at the time of the solstice and was connected with the Mithras cult. As such, these celebrations were accompanied with heavy feasting, and it seems that this element might have been transferred without hindrance into the celebrations of Christmas, although the traditional period for the saturnalia was turned into a period of fasting leading up to a period of feasting (commencing on the 25th) This is usually termed “ the History of Religions Theory”. A counter-argument, which has been proposed, is that the date was set by calculating nine months from the 25 March, the date of the vernal equinox, on which the Annunciation was celebrated (The so-called “Calculation Theory”).
A third reason might have been the need to separate the feast of the nativity from the feast of epiphany after the Council of Nicaea in AD 325 had condemned the doctrine of adoption – Jesus was not to be considered “revealed”; instead he was to be considered incarnate, that is born. Hence a date of birth had to be marked, superseding the feast of Epiphany, which may have come first; but celebrations of Epiphany on the 6th of January continued to be considered celebrations of the birth of Jesus in the 4th century and a general practice seems not to have been finely established before the 6th century. One significant event took place in AD 567, when the council of Tours proclaimed the twelve days from Christmas to Epiphany as a sacred and festive season, and established the duty of Advent fasting in preparation for the feast.
It is probable that all three sets of hypotheses contributed to the early liturgical development as well as the later popularity of the feast.
At first, the feast was probably not considered especially significant when compared to the Easter celebrations. Indeed, until the 7th century it was formally listed among the feasts of the martyrs and not as a major feast. It was not until Pope Leo I (AD 400 – 461) around 440 called it a sacrament (sacramentum nativitatis Domini) that it became established as such; as opposed to this Augustine (AD 354 – 430) had “only” called it a memoria, although he did claim it in a sermon (no.184) that it was a major feast, while Pope Leo I (c. AD 400 – 461) named it a sacrament. The intense preoccupation with the sacrality of the incarnation of Christ pervades the sermons of Leo as he vehemently argues against the different unorthodox teachings like adoptionism and other anti-incarnational belief systems. 
A Popular Feast
At this point we get an inkling of how the feast was not only turned into one of the major events in the Christian church, deserving of special celebrations.
One of the best descriptions can be found in the Christmas morning sermon of John Chrysostomos, who writes how his ears resound to the shepherd’s song, “piping no soft melody, but chanting full forth a heavenly hymn.” Later he writes how he too desires to rejoice: “I too wish to share the choral dance, to celebrate the festival. But I take my part, not plucking the harp, not shaking the Thyrsian staff, not with the music of the pipes, nor holding a torch, but holding in my arms the cradle of Christ. For this is all my hope, this is my life, this my salvation, this my pipe, my harp. And bearing it I come, and having from its power received the gift of speech, I too, with the angels, sing: Glory to God in the Highest ; and with the shepherds, and on earth peace to men of good will. 
Thus, as soon as Christmas Mass had been celebrated, we get glimpses of a joyous time. For instance, Gregory of Tours (Ad 538 – 594) tells us in passing how “Sichar, the son of John, was enjoying himself in the village of Marthelan, as part of the Christmas festivities with Austregesil and a number of other local folk, the village priest sent one of his servants to invite some of the men to come and have a drink in his house…  As the story goes, these Christmas celebrations turned into a major feud which did not end before Sichar’s home had been burned down and robbed, at which point a peace was negotiated between the two feuding parties.
It is thus perhaps not only a matter of righteous convention, when Caesarius of Arles (AD 470 – 542) complained that “There are some people, who come to the birthday festivals of the martyrs for this sole purpose, that they may destroy themselves and ruin others by intoxication, dancing, singing shameful songs, leading the choral dance, and pantomiming in a devilish fashion. 
But all was not just heavy drinking. From a fragment of a poem by Venantius Fortunatus, (c. AD 530 – 600/609) we possess a description of the traditional Christmas fare in 6th century Merovingian France.
“Today I celebrated the festive day, on which the holy birth of the Lord came upon this earth. First from all directions came cheese – then came rounded wooden salvers – a dish adorned on all sides bore meat and fowl – who in a moment offer food for all on your lips, and from all”. 
The period leading up to the Christmas celebration may have been marked by a prolonged fast. But in the end, joyous festivities seem to have marked the day.
Drikke Jul – Drinking Yule
Ultimately, the probable linkage between the celebrations of solstice and the nativity of Christ, seems to have penetrated the murky and cold hinterlands behind the Rhine and up north into Scandinavia. At least, this has made it complicated to define the elements of the traditional non-Christian Yule-celebrations, which we occasionally get a glimpse of in the skaldic poems and other sources.
In itself, the word “Jul” or “Yule” is first known from a fragment of a Gothic Calendar (Cod. Ambrosianus A) from the beginning of the 6th century preserved in Milan. The text reads: Naubaimbair: fruma Jiuleis, which can be translated as either: November, the first Yule month; or, alternatively: November, the month before Yule. In Old English, the expression: Æftera Gēola, denotes January. In itself, much ink has been spilled on finding the etymology of the word, but so-far no explanation has been universally accepted. What we know is that the word Yule undisputedly entered the Finnish language before Christianisation, designating “feast”, and that there are non-Christian roots to the word. Neither is there any doubt that the word denoted festivities taking place around winter-solstice both before and after the Christianisation of the people east and north of the Rhine. Even today, it is the word “Jul” is universally used in the Scandinavian, Estonian, Frisian and Dutch languages; it is, of course, also known from Old English.
A number of sources are often quoted concerning the exact form and content of the pre-Christian festivities, but the main source – the Haraldskvæđi or Hrafnsmál from c. 900 – only mentions the element drink. Here it tells us about king Harold Fairhair:
One of the few traditions which must by all accounts be considered pre-Christian, is the formula “til árs ok til friðar”, where árs means a good year of growth and harvest, while friðar means peace among friends and perhaps also good luck in bed. This was the formula used when lifting up the drinking horn and passing it around. A version, still in use in Denmark is “ lad jule-freden sænke sig” (let the peace of yuletide settle [upon us].
Nevertheless, it is generally believed that yuletide-celebrations may also have included some sort of bloody sacrifice. This is based on different sources. One indication is presented bythe enigmatic concept, Freyr’s game, in the poem above. Some scholarsbelieve that the kenning refers to a tradition mentioned in Hervarar saga ok Heiðreks and in the prose segment in “Helgakviða Hjörvarðssonar”, in which we hear about the sonargǫltr where a boar was sacrificed on Yule eve after the people had laid their hands on it to swear at the king’s toast – bragarfulli. The pagan god, Freyr was known to ride a gold-bristled boar, and Frey’s game may thus allude to this tradition of swearing in while the chieftain exclaims his “til árs ok til friðar”!  Another reference worth mentioning might be the Ágrip, (Ágrip af Nóregs konunga sögum) from c. 1190 where it is told about Olav Tryggvason that he dispensed with sacrifices and the sacrificial drinks and in accordance with the wishes of his people exchanged these with festive drinking at Christmas, Easter, St. John (summer) and autumn-beer at St. Michael.” However, most sources are late and any firm conclusions cannot be drawn although modern Asa-believers staunchly believe this.
Whether or not these celebrations included games, general amusements and mummer’s dancing – as was the case later on – is everyone’s guess. Perhaps, though, it is appropriate to remember the 10th century text, which describes a Christmas party at the Byzantine court. Here four “Goths” took part carrying masks and clad in tunics or gowns made of pelt with the hair on the outside. In their left hand they held a shield and in their right a rod. Running into the presence of the Emperor in his great dining-hall, the men would beat their shields with the rods and yell “Yule, Yule”. Later they would be expected to read aloud the so-called “Gothic” song – a mixture of babbling and praise of the emperor. It is believed that the “goths” featuring in these ceremonies were played by the Varangians, the Scandinavian soldiers serving in the lifeguard of the Emperor.
The earliest record of a Christmas Mass at midnight can be found in the pilgrimage of Egeria from AD 381 – 384 in which she writes that she first partook in a vigil in Bethlehem. Afterwards, the faithful walked to Jerusalem, to Golgotha, where a festive mass was celebrated in the morning. The walk was no more than ten km. but it took some time as the monks and priests walked barefoot.
It is probable that this order with first two and later three masses was copied in Rome in the 5th – 6th century. Around this time St. Mary Major was rebuilt by Sixtus III, who had a replica of the birth grotto designed in the crypt. Later, in the 7th century the church acquired a substantial part of the relics of the true crib or manger and this led to the tradition, celebrating the so-called “Mass at Night” there. The second mass – in the morning – would celebrated at St. Anastasia, while the third mass held in St. Peter’s.
When Gregory the Great confirmed it around AD 591 – 92, he mentioned three masses; added to this should be the vigil celebrated on Christmas Eve proper. Thus the full set included four stations: at St. Mary Major in the evening, at the Crèche nearby during the night, in the morning at St. Anastasia and finally (to reduce the burden of walking to St. Peter) the Christmas Mass in St. Mary Major. Later this was made obligatory by the Carolingian reforms. Since then, the readings have been as follows: Christmas Eve: Matthew 1.18 -21, Midnight Mass: Luke 2:1 -14, Christmas Mass at Dawn: Luke 2:15 -20, Christmas Mass during the day: John:1 :1-14
But also the following days acquired their own liturgical importance: St. Stephen was commemorated on the 26th, St. John the Evangelist on the 27th, and Kong Herod’s massacre of the Holy Innocents on the 28th of December. This was also later called Childermass and came to be the time for the famous “feast of Fools”. 
The Christmas Plays
Some time in the 10th or 11th centuries the tradition evolved to turn part of the celebrations into a drama. It is generally believed that this developed out of the Easter tradition, which seems to be an enactment of the quem quiritis – dialogue (c. 950, St. Gallen). However, very soon – or perhaps around the same time – there are signs of a development of a parallel Christmas play based on the dialogue in Luke, but encompassing elements from Genesis and the prophets. A full liturgical movement would thus be set in movement on the 24th – which was the official day set aside to commemorate Adam and Eve – with a play enacting the Creation, Fall and Expulsion as well as the heralding of the prophets pointing towards the Christmas as well Easter
Soon, however, the celebrations came to focus increasingly upon the incarnation and the childhood of Christ, nourishing the popular piety through mystery plays. It is generally believed that these developed out of the Easter tradition and that the earliest evidence dates from at least the 10th century. The basis of this tradition seems to be an enactment of the quem quiritis – dialogue (c. 950, St. Gallen). Very soon – or perhaps around the same time – there are signs of a development of parallel Christmas plays based on the dialogue in Luke, but encompassing elements from Genesis and the prophets, leading towards the reenactement of the nativity scene in the midnight mass.
Finally, in AD 1223, Francis of Assisi set up a manger in the grotto at Greccio, surrounded it by live animals and filled it with straw. An lo and behold, come midnight the miracle happened and the manger was filled with a live baby. Out of this grew the medieval tradition of setting up and venerating tableau’s, like the one by Arnolfo di Cambio from 1289, originally intended to populate the copy of the crèche in St. Maria Major.
Some of these Christmas and Nativity plays were punctuated by hymns, which are still in use. One such is the hymn, Puer natus in Bethlehem (A child is born in Bethlehem). Originally a Latin text from the 13th century, it has been translated into a number of languages, of which a German translation from 1439 is the first. Still cherished today, it reminds us of the grand spectacles which have now been transformed to school plays. However, numerous other hymns deserve to be mentioned from early Christmas hymns written by poets in the 4th century to the famous Latin hymns of the high middle ages, resulting in the treasure trove of English Carols as well as German and Scandinavian post-reformational hymns. 
 Toward the Origins of Christmas. By Susan K. Roll, Publisher: Kok Pharos Publishing House 1995, p. 213 -14)
 Toward the Origins of Christmas. By Susan K. Roll, Publisher: Kok Pharos Publishing House 1995, p. 211 – 213)
 John of Chrystostom, In natalem Christi Diem, Migne Patrologia Graeca, vol 56, Col 385-394. Translation by Maria Dahlin: The Centre of All Festivals. A Translation and analysis of Chrysostom’s Christmas Sermons. Thesis, BA 2012
 Gregory of Tours: The History of the Franks. translated with an introduction of Lewis Thorpe. Penguin Books 1974, pp. VII.46 p. 428.
 Caesarius, Sermo 55:2. Quoted from: Culture and Religion in Merovingian Gaul. Ad 481-751, By Yitshak Hen. Brill 1995, pp. 87)
 Venantius Fortunatus (c. 530 – 609), appendix 11. Transl. from Venantius Fortunatus: Personal and Political Poems. By Venantius Hoborius Clementinus Fortunatus. Ed. and transl. by Judth W. George. Liverpool University Press 1995
 Transl. from: Old Norse Poems: All the non-Skaldic verse not contained in the Eddas. By Lee M. Hollander. Columbia University Press 1936, p. 121
 Helge Rosén, “Freykult och Djurkult”, Fornvännen 1913, pp. 213–44, pp. 214–15,
 Jul. By Anders Hultgård. In: Germanisches Altertumskunde Online (Vol 16), De Gruyter 2000
: En germansk julfest i konstantinopel på 900-talet. By N. Sjöberg. I: Fataburen. 1907, pp. 31 -35
 Egeria and The Fourth Century Liturgy of Jerusalem. Hypertext version developed by Michael Fraser, Department of Theology, University of Durham. June 1994.
 The Liturgy and Time. By Irénée Henri Dalmais, Pierre Jounel, Aimé Georges Martimort. Liturgical press 1986, p. 83 – 84)
 Francis of Assisi. By Chiara Frugoni. Continuum 1999, pp. 114 ff.
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Weihnachten/Eeihnachtsfest/Weihnachtspredigt. In: Theologische Realenzyklopedie Online. De Gruyter
Jul. Kulturhistorisk Leksikon for Nordisk Middelalder. Vol 8. Rosenkilde & Bagger 1981.
Weihnacht. Lexicon des Mittelalters. Vol 8. Verlag J. B. Metzler 1999
Das Weihnachtsfest (Religionsgeschichtliche Untersuchungen, part 1)
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Die Anfänge von Weihnachten und Epiphanias: eine Anfrage an die Entstehungshypothesen
By Hans Förster
Mohr Siebeck, 2007
Weihnachten in der Musik: Grundzuge der Geschichte weihnachtlicher Musik.
von Helmut Loos
Gudrun Schröder Verlag 1991
Christmas Customs and Traditions, Their History and Significance
Clement A. Miles
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The Origins of Christmas
by Joseph F. Kelly
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Toward the Origins of Christmas.
By Susan K. Roll
Kok Pharos Publishing House 1995
Mosaics in santa Maria Maggiore: the Nativity. Source: Wikipedia