From Maurice Keen, Chivalry (1984), 61-62:

But the aim is not, in either version, to present such a sharp dichotomy

as we find in Bernard between the profligacy of worldly knighthood and

the religious commitment of true Christian chivalry; rather it is to

distinguish between degrees of virtue in knighthood, in the same way as

Baudouin de Conde and Geoffrey de Charny seek to distinguish scales of

chivalrous achievement and virtue. Lancelot may be tainted by his adulterous

love for Guinevere, but he is a great Christian knight and in the Queste

has his glimpse of the Grail, even though he does not see it openly. . . .

The significance of the Grail legends lies not in any contrasting of worldly

with religious chivalry, but in the way in which they carry us, through stories

of martial adventure, on to something beyond. The quest that they describe

is not just for the Grail, as an object, but for what it symbolises: eucharistic

grace and communion in ecstasy with God. The distinctive feature of the stories

centring round it is that these spiritual things are presented as the ultimate

goal and prize of the elite of knighthood: the idea of the knight errant seeking

adventure and the quest for union with God are as it were fused together. As

Frappier has put it, what the Grail romances express is not so much an ideal of

knighthood in the service of religion but of knighthood as a religious service in

itself. Herein lies their special significance for the historian of the chivalrous mentality.

The church authorities were consistently cautious in their approach to the story of the Holy Grail, neither accepting nor condemning it, leaving the whole matter in the limbo of legend. Their caution is not surprising. Despite the profoundly religious spirit of the Grail romances, they reflect attitudes that are strikingly non-sacerdotal. The liturgy of the Grail is given the setting not of a great church but of the hall of a feudal castle. . . .Among the clergy of the stories, the figures whom we most often encounter are hermits, solitaries whose way of life is just about as divorced as may be from the world of the organised ecclesiastical hierarchy, and most of them prove to be men who, until they felt the strength to bear arms ebbing from them in the autumn of life, had followed the vocation of knighthood. The commission of the 'good knight' Joseph of Arimathea comes to him not through the apostolate of the genuine gospels, which in the middle ages was commonly taken to prefigure the Christian priesthood, but from Christ himself, directly. Secular ideas about lineage have moreover made a deep impression on the manner in which Joseph's office and that of his descendants as guardians of the Grail is treated. Indeed, the whole Grail story is in one sense the history of a knightly lineage . . .a line pre-elected by God to fulfil a special mission.

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To the historian of the chivalrous mentality, the importance of the Grail romances . . . is the way in which they reflect accurately the confidence of Christian knighthood that its way of life was one pleasing to God and chivalry and order instituted directly by him. The Grail romances have a particular importance in this context because the incidental adventures that crowd their pages remind us that this was not an idea confined to the narrow frame of reference of the crusade but one to which all chivalrous activity was seen equally as relevant: the loyal service of an honoured lord or beloved lady, the succour of the unjustly oppressed, the hardships of the knight errant on his travels, and even endurance of the trials of joust and tourney, as well as the defence of the Holy Places. . . . [what they are] implicitly claiming here is that there is no need to try to prise apart the goals of worldly honor and of service acceptable to God, that the knightly life, with its violence and with all the richness and decor of its aristocratic trappings, is within its own terms a road to salvation.