On one hand, every day finds groups of pilgrims singing hymns while gathered around picnic tables in the grounds of the Dublin 4 complex, or attending music-filled Masses in the arena.
There is a relaxed, festival feel (albeit a sedate festival largely consisting of senior citizens), as the pilgrims wander in and out of the myriad workshops or browse the maze of stalls.
But in another room yesterday a discourse on the dark side of the Catholic Church was taking place, dealing with the clerical sex abuse scandals which have cast (and which continues to cast) a long, sorrowful shadow over the organisation.
And the prelate selected to grasp this thorny topic was the Archbishop of Manila, Antonio Tagle.
His audience included several cardinals from the Vatican, and also the Bishop of Raphoe, Philip Boyce (the diocese was heavily criticised in a report last year into clerical sex abuse), the Bishop of Kilmore, Leo O'Reilly and auxiliary bishop of Dublin, Eamonn Walsh who offered his resignation in the wake of the Murphy report in 2009, but it was not accepted by the Pope.
The title of the speech was: 'The Abuse of Children: Accepting Responsibility, Bringing Healing' and from the outset Bishop Tagle stated that he was speaking specifically about the issue from an Asian point of view.
But really many of the points he made were applicable to the West. He described the crisis as "immense in scope", including "allegations of sexual misconduct, suspicions about the clergy's handling of money, accusations of misuse of authority, inappropriate lifestyle and a host of other things," he said.
"To pretend that no problem exists does not help."
Bishop Tagle explained how cultural differences meant that Asian victims of sexual abuse often remained silent.
"For Asian cultures, a person's shame tarnishes one's family, clan and community. Silence could be a way of preserving what is left of one's honour, it could also be a sign of trauma," he said.
He also pointed out that the church's relationship with the media needed to be reassessed.
"Media practitioners observe that when they report on abuses committed by politicians, financiers et cetera, the church appreciates them -- but when they expose anomalies within the church they are banded as anti-church and anti-Catholic, even if their information comes from people close to the church."
He also discussed the reaction of bishops to the ongoing scandals.
"They feel lost when a cleric commits sexual abuse -- they cannot defend the priests while neglecting truth, justice and the good of the victims and the community," he explained.
But right at the end the bishop was overcome with emotion as he lamented the numerous ways in which children are exploited in Asia, including "a booming sex tourism that attracts paedophiles, the kidnapping and selling of children, the trading of body parts of children, child labour of slavery," he said, as he struggled for composure as his eyes filled with tears.
There is a sense that the church hierarchy is anxious to concentrate on the light rather than on the dark during this Congress.
The event's secretary general, Fr Kevin Doran, confirmed that no senior member of the Irish clergy is scheduled to address the issue during the week-long congress.
And after much talking, singing and praying behind the walls of the RDS, the Eucharistic Procession will be doing a circuit around the Dublin 4 complex this evening.
Outside the Four Seasons Hotel yesterday afternoon, a group of colourfully-clad pilgrims were standing at a bus-stop, belting out 'Ave Maria'.
"We're practising for the parade," once cheerfully said, looking on the bright side of life.