ROME — All of a sudden at the 2014 Synod of Bishops on the family, “gradualism” as a concept in both Catholic moral theology and pastoral practice, which not so long ago seemed on the verge of being stricken from the official lexicon, is back with a vengeance.

There have been multiple references so far to the “law of graduality,” more commonly referred to by theologians over the years as “gradualism.” Its apparent popularity may offer a clue to how things are evolving in the keenly watched debate over divorced and remarried Catholics, but understanding why requires a bit of background.

At one level, gradualism is no more than the common sense observation that virtues such as honesty and courage aren’t all-or-nothing propositions, and that people move towards them through stages and at different speeds. It implies that just because someone’s current situation falls short of perfection doesn’t mean it has no moral value, and it’s often better to encourage the positive elements in someone’s life rather than to chastise their flaws.

It was probably that sense of gradualism Pope Benedict XVI had in mind in 2010 when he said in an interview with a German journalist that if a male prostitute uses a condom to try to avoid infecting people with HIV/AIDS, it can be “a first step in a movement toward a different way, a more human way, of living sexuality.”

Benedict wasn’t repealing the church’s opposition to condom use, but he was saying that there are times when it suggests a concern for others which, in itself, is laudable.

Where gradualism becomes more of a bone of contention is when it’s invoked to justify a permissive approach to moral rules.

For instance, some theologians and even a few bishops over the years have invoked gradualism to defend going easy on Catholics who practice birth control, arguing that while the teaching of Pope Paul VI in 1968’s Humanae Vitae reaffirming the traditional ban represents an ideal, there may be valid reasons why lots of people can’t be expected to fully embrace it right now.

For those concerned with defending tradition, this second sense of gradualism can make it sound like another word for “relativism”, meaning watering down objective standards of morality. By the same token, it also makes gradualism a favorite refuge for moderates who accept the content of Church teaching, but who don’t want to go to war over it.

Ferment over gradualism, and what its implications may be, tends to arise whenever the Catholic Church ponders sexual morality.

The last time the Vatican staged a Synod of Bishops on the family, which was almost 35 years ago in 1980, talk about gradualism was in the air, too. Pope John Paul II was sufficiently concerned about where it might lead that he included a warning in a homily he gave for the closing Mass of the synod, a line he then also dropped into the meeting’s concluding document, Familiaris Consortio.

“What is known as ‘the law of gradualness’,” John Paul said, “cannot be identified with ‘gradualness of the law’.” The gist was there’s just one set of rules for everybody, and they’re not going to change.

Since that time, the Vatican has occasionally circled back to the theme. When the Pontifical Council for the Family put out a guide for priests hearing confessions on matters having to do with married life in 1997, it warned that the “law of graduality” shouldn’t induce priests to send the signal that sin isn’t still sin.

Especially in that context, it’s striking how often the “law of graduality” has surfaced already at the 2014 edition of the synod.

In his opening address on Monday, Cardinal Péter Erdő of Hungary argued that Humanae Vitae should be read in light of graduality. In a session with reporters at Vatican Radio Monday night, Cardinal Reinhard Marx of Munich invoked graduality as a key to helping the church develop a new way of talking about sex.

In a briefing session for reporters on Tuesday, a Vatican spokesman described graduality as among the synod’s emerging themes, and Cardinal Vincent Nichols of the UK said the idea of graduality “permits people, all of us, to take one step at a time in our search for holiness in our lives.”

Here’s why the vocabulary matters: Everyone knows that the hottest issue at this synod is the question of whether divorced and civilly remarried Catholics ought to be able to receive Communion. Moderates supporting that change need to find a way to justify it that doesn’t seem to call into question the principle that marriage is for life.

“The law of graduality” could be one way of doing the trick, and thus references to it could be understood as an early show of strength for the moderate position.

It’s also perhaps an index of how things have changed under Pope Francis that bishops feel licensed to use the phrase without a truckload of qualifications, given the increasingly disapproving tone of most Vatican statements on it in the recent past.

In other words, the sudden return of gradualism may be a central part of the storyline about the 2014 synod.