There are some key ways that a "provisional culture" can affect people's marriages, he said. For example, grounds for annulment can include when "a person might directly and principally intend against a permanent marriage."
"That is to say," he continued, "'I marry you but I intend to end this perpetual union when I see fit'." This can't just be an admitting that divorce "happens," he noted, but rather "an intention against the permanence of the marriage" at the time of the wedding vows.
Another nullifying factor is "ignorance" of the nature of marriage as "a permanent union between a man and a woman, that in some way is ordered to the procreation of children through sexual cooperation," he said.
"We presume that everyone who has achieved puberty is not ignorant of marriage. The law of the Church says we're supposed to presume that," he said.
So for ignorance to nullify a marriage, "you have to prove in a definitive way that they really had no knowledge of the concept of marriage as a permanent union." And this would be ignorance of a "basic human understanding" of marriage, Flynn clarified, not an ignorance of graduate-level theology of marriage.
Also, a person's "grave" psychological defects or a "grave defect in their will or in their cognition" can be factors mitigating a person's "ability to choose" to marry someone, he said. And this has a higher risk of happening in today's culture.
He acknowledged that "it is true that in a breakdown of the family, in a 'provisional culture,' in the 'culture of death' as John Paul II said, it's more likely that people's ability to choose the act of marriage will be mitigated."
There are other factors that can nullify a marriage as well. One question is if someone is "free to enter into the human relationship of marriage," Flynn said.
"In other words, are they capable of having a human relationship at all with other people, or do they suffer psychologically in a way that they wouldn't be able to?"
Another question is, "Does a person reserve to themselves the right to create children in an intentional way?" Flynn asked.
Although the Church teaches that contraception is gravely wrong, using it does not make one's marriage invalid, he clarified. For that to be the case, someone "has to intend, directly and principally and definitively, not to grant the other person the right to the good of children. Not to be open, in any way, at any point in the marriage, in a definitive sense, to children."
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Furthermore, if a person takes their wedding vows with the definitive intention not to be faithful, the marriage would not be valid. This is different than a case of someone vowing to be faithful and then cheating on their spouse later, he clarified.
The Church's annulment process is thorough, he said, and for good reason.
"It's very difficult to kind of mete out what a person had intended on their wedding day, which is why the Church's process for a declaration of nullity is so exhaustive," he said, "and why it's often the case that it's difficult to come to a conclusion."
"Because you have to go back to an earlier time and get real testimony about what a person's capacity was or what their intentions were," he added.
Other present-day marital problems Pope Francis mentioned are couples who are living together in a sexual union before marriage, and couples who are expecting a child before marriage, and who are rushed into marrying in a "shotgun wedding" rather than "accompanied" by the Church in order to spiritually "mature."
Mary Rose Verret, who with her husband Ryan runs the "Witness to Love: marriage prep renewal ministry," emphasized the importance of the Church teaching these couples about Christian marriage, and ensuring they are living in accord with Catholic teaching and are ready to receive the sacrament before they make their vows.