The Catholic Church now has a job ahead of itself explaining to people its new annulment procedures. I've never heard the circumstances under which a marriage may be annulled formally explained. I doubt if very many others have heard it explained either.
For the most part, what information you do pick up about it is by a kind of osmosis. For example, that non-consummation is a ground for annulment. You hear every now and then the accusation that an annulment is 'divorce, Catholic-style'.
If you've been paying attention more than most, you might have heard that for years it was easier to get an annulment if you live in America than in most other countries. Or that even within America, you could get an annulment in one diocese more easily than in another.
In fact, at one point the US accounted for fully 80pc of all annulments granted worldwide, even though America accounts for just 6pc of all Catholics. Between 1982 and 1984, the Vatican overturned 80pc of the American annulment rulings it reviewed.
One annulment it famously overturned was that of Sheila Rauch Kennedy, wife of Joe Kennedy, oldest son of Bobby Kennedy.
Joe wanted an annulment. Sheila didn't. She wrote a book about the break-up of her marriage and the annulment battle. It became a best-seller.
In truth, though, the chances are that you know little enough about annulment because there has never been a formal effort on the part of the Church to properly acquaint Catholics with it.
That is going to have to change now that Pope Francis has relaxed the annulment rules to make it easier, faster and cheaper to get one.
The bishops are also going to have to get ready for a possible upsurge in annulment applications. If there is an upsurge, it will be a reversal of present trends in Ireland. In 1998, there were just shy of 600 applications around the country. By 2007, this had dropped to 332 and by 2013 to 231. So that's a drop of almost two-thirds in just 14 years.
What's going on? Probably fewer people could be bothered applying than in the past. One possible reason for this is that it has heretofore been so hard to get an annulment. But that has always been the case. The main reason is probably that many Catholics, including practising Catholics, don't feel the need to get one. They simply separate and, if need be, divorce and remarry via civil law without going near the church.
This is a symptom of the growing secularisation of the country and as a consequence of this a dimming knowledge of what an annulment is all about.
It's also a consequence of a diminishing awareness of what a sacramental marriage is. Two-thirds of Irish people still marry in church. That's much higher than the level of practice in the country, especially among the age group most likely to marry, people in their thirties.
Many couples choose to marry in church because of a cultural connection with their religion that often doesn't go very deep or because churches are generally pretty places to marry in, or both.
How seriously they take the religious dimension of their marriage is another question. How well they understand that they are marrying in the eyes of God is open to doubt.
Has it been properly explained to them that a sacramental marriage in the Catholic Church brings into being an indissoluble bond and that your spouse can no more cease to be your spouse than your sibling can cease to be your sibling, no matter how you feel about them?
How many know that a Christian marriage must be open to the possibility of children?
That is, how many who marry in church really believe that marriage is much more than an emotional bond between two adults that needs last only as long as both spouses feel that emotional bond?
Who knows? But according to Germany's Cardinal Walter Kasper, Pope Francis believes that up to half of Catholic marriages may be invalid because of a deeply flawed understanding of what marriage really is.
This very high estimate has been strongly challenged, but even if 50pc is a big exaggeration, it remains the case that probably more Catholic marriages can be annulled than we think. If so, then it is right for the Pope to make the process easier.
A declaration of nullity, by the way, is a declaration that the marriage never existed. Therefore, it is not like divorce. It's a bit like when someone is able to void a contract because it was entered into improperly.
A person may have been forced to enter into the contract, in which case they didn't give their free consent to it. They may have been misled about the nature of the contract or they may not have been in a fit mental state when signing the contract, meaning once again that they didn't enter into it freely.
In none of these cases have they broken the contract. The contract never really existed.
It's the same when a marriage is annulled and the grounds for annulling a marriage are not entirely dissimilar to the reasons a contract can be voided. A big reason is that the marriage wasn't entered into freely and with full and proper consent on the part of one or both parties to it.
By the way, the cost here of going through the annulment process is low, especially compared with getting a divorce in the civil courts and in half of cases nothing at all is paid.
This reform is all part of Pope Francis's efforts to make Catholic rules less burdensome and more merciful.
The annulment reforms are worthwhile but could easily be mishandled and bring the whole system into disrepute. In the end, each individual bishop is going to have an awful lot more discretion over how annulments are handled and whether they are granted in his own diocese.
Suppose in the name of 'mercy' a given bishop makes it easy to be granted an annulment? This would sow huge confusion and uncertainty among other Catholics as to whether their own marriages were valid.
Then you might have another diocese that is much stricter. The word would get out that it is easier to get an annulment in this diocese than that diocese and the whole system would come to seem very arbitrary and inconsistent.
Imagine a legal system in which too much depended on the individual disposition of the judges. This is a factor, obviously, but shouldn't be too big a factor.
So the challenge now for the church is to properly inform Catholics about the whole annulment process, set in place a system that works well and ensure there is uniformity and consistency between dioceses that strikes a proper balance between mercy and a standard set sufficiently high that the whole annulment process isn't abused and brought into disrepute.