In recent years, the name Duggar has gone from a synonym for a certain brand of squeaky-clean family-friendly entertainment to something very different.
These days, the name is polarizing at best, or at worst, a byword for the sort of hypocrisies and scandals often found at the heart of the most secretive cults.
It's impossible to separate the family's controversial religious beliefs from their rise to the the near-top of the reality TV totem pole.
After all, a great many of the practices that have made the Duggars fascinating to millions of outsiders are rooted in their faith.
Of course, it wasn't so long ago that the same belief system nearly brought the Duggar empire tumbling down like the walls of Jericho.
For as much as we know about some specific details of the Duggar creed (sex is for procreation between man and wife only; women are forbidden to wear pants or hold jobs, etc.), a lot of the larger questions regarding their religion remain sources of debate and speculation.
For example, the biggest Duggar-related mystery of all may be a simple but profound one, and have more than one answer:
What religion do they even practice exactly?
The family has been accused of giving misleading answers when asked the simple question of what faith they belong to.
Remarkably, it's a question that you'll never hear the Duggar kids - even the grown, married adults - fielding publicly.
Instead, they defer to Jim Bob, who's stated (on the rare occasions he's addressed the issue himself) that he and his family are Independent Baptists.
Despite their name, Independent Baptists are an ultra-conservative lot with little tolerance for personal freedom.
They exist on the fringes of American Christianity, and are not a recognized sect, so much as a loose network of individual congregations.
Ultra-conservative televangelist Jerry Falwell abandoned the Independent Baptist Church for the more moderate Southern Baptists.
That should tell you all you need to know about how extreme the IB belief system is.
Amazingly, the Tontitown, Ark., family falls far to the right of even the most conservative Independent Baptists on most issues.
This has led many to the conclusion that Jim Bob is taking his cues from somewhere other than the leadership of the IB Church.
To answer the question of where the most extreme Duggar beliefs and practices originate, we need to turn our attention to the Quiverfull movement.
There's debate as to who founded the movement, but it's widely agreed that Quiverfull was popularized by the Reverend Bill Gothard in the late 1970s.
In 2015, Gothard resigned in disgrace from his post with the Quiverfull-centered Institute for Basic Life Principles amidst a flurry of sex assault and harassment allegations.
He and his organization have shelled out an undisclosed amount of cash to keep the accusers at bay, but dozens of new allegations have surfaced.
In just the past couple of years, the movement's extreme right-wing beliefs have received such negative attention that the Duggars are keeping their distance.
At least to the point where they're hesitant publicly associate with the Quiverfull movement, though there's no question that they adhere to Gothard's teachings.
First and foremost, the Duggars use Quiverfull teaching materials in homeschooling their 19 children (and counting).
They also refer to the spiritual teachings of this movement when addressing topics such as sex and sexual abuse:
After the first of Josh's two sex scandals, which involved the molestation of five young girls, including his sisters, the family tried to deal with it "in-house."
When they sent Josh Duggar to rehab after he was outed as an Ashley Madison client, they chose a faith-based facility with the approval of Gothard's IBLP.
The Duggars cut ties with Gothard (publicly, at least) following allegations that he groped and assaulted dozens of young male and female employees.
Prior to that, they called the religious leader a close family friend and "an inspiration" as recently as 2014.
The most telling sign that the Duggars are Quiverfull devotees, however, is the fact that it was Gothard who first espoused the notion that defines them:
That is the duty of Christians to have as many children as physically possible.
This is a fundamental principle, explains USC assistant professor of religion Cavan Concannon, according to In Touch Weekly:
“In the Quiverfull movement, your kids are blessings from God and they are also weapons in the culture war."
"Some people in the movement would say that part of having a lot of kids is an attempt to birth more conservative Christians in a world that doesn’t have enough of them.”
Some have wondered how the Duggars can reconcile their wealth and fame with their devotion to a religion that preaches the importance of poverty and humility.
(Recently, Jessa Duggar teaching a seminar on how to dress and act modestly - while charging $20-50 a ticket - illustrated this disconnect.)
Simply put, they see themselves as soldiers in an apocalyptic culture war, and they believe that TV is the most important weapon in their arsenal.
Jesus Christ famously said, "The meek shall inherit the earth."
But Bill Gothard basically said, to read between the lines:
There's power in numbers, so let's tailor my beliefs to help me expand my following through procreation and mass media to boot.
While they often talk about putting God first, the Duggars have left little mystery as to which of these messages they value more.