Her argument (according to newspaper reports) is that infidelity is essential to the psychic functioning of some men, making infidelity "almost unavoidable". If this were accepted it could be "very liberating" for women.
But her argument goes much further than this, it becomes much more radical. She claims that those men who are faithful might have something wrong with them - that they might be suffering from a pathology, a too rigid concept of duty:
However, in Miss Vaillant's book she insists that fidelity is not, by definition proof of love. In fact, "pathological monogamists" in many cases lack the strength of mind to take a mistress, she claims.
"They are often men whose father was physically or morally absent ... during their childhood. These men have a completely idealised view of their father and the paternal function," she said.
"They lack suppleness and are prisoners to an idealised image of a man of duty."
She has inverted the normal view of fidelity. Now it is the faithful men who are weak for not taking a mistress and immoral for following a principle of duty.
What's going on here? I don't have a chance to read the book, but it does seem as if Madame Vaillant is taking a liberal argument to a more radical conclusion. In the liberal view, the moral thing is to be self-sovereign and to do what we will. Therefore, the aim of reform is to remove impediments to our individual choice.
The older morality becomes one of these impediments. It's too rigid - it states clearly that the aim is to be faithful. This restricts what we can choose for ourselves. It makes us a "prisoner" to our sense of moral duty.
The hero is then the one who breaks through moral taboos (impediments). So it is the adulterer, in Madame Vaillant's eyes, who is the healthy one with the strength of mind to act for his own purposes.
It's true that liberalism also states that our actions must not limit the similar freedom of others. But, according to Madame Vaillant, women can find it liberating to accept that their husbands need to have a mistress. So adultery passes that little qualification.
I won't embark here on a defence of fidelity as an ideal in marriage. My intention has simply been to point out how radical liberalism is when applied consistently to such issues. However, there is one curious flaw in Madame Vaillant's argument that's worth pointing out.
According to her, faithful men suffer a pathology because their fathers were absent during their childhood. So father absence is recognised as a bad thing - a source of pathology. But wouldn't men taking mistresses create more father absence in society? Most men find it hard enough to combine a career and family. What if they have to combine career, family and mistress? Won't they be spending less time with their kids? So wouldn't then adultery (the supposedly good thing) create more father absence (the bad thing, the source of pathology)?
All of which raises another question. Does liberalism at least leave people alone to do their own thing, even if it does so by rejecting or inverting normal moral standards? The answer clearly is no. It does not even achieve this. Far from leaving people alone in their relationships, it is extraordinarily intrusive.
For example, the French government has announced it will introduce a new law which bans 'psychological violence' in relationships. A man might end up with a criminal record if he insults his wife during an argument:
Married couples in France could end up with criminal records for insulting each other during arguments.
Under a new law, France is to become the first country in the world to ban 'psychological violence' within marriage. The law would apply to cohabiting couples and to both men and women.
It would cover men who shout at their wives and women who hurl abuse at their husbands - although it was not clear last night if nagging would be viewed as breaking the law.
The law is expected to cover every kind of insult including repeated rude remarks about a partner's appearance, false allegations of infidelity and threats of physical violence.
French Prime Minister Francois Fillon said electronic tagging would be used on repeat offenders.
The law makes every adult person in France a criminal. Who hasn't at some time shouted at or insulted a spouse during an argument?
It's possible that the law might catch out some of those men who do systematically bully their wives. But it does so in an incredibly intrusive way, by criminalising behaviours that occur in nearly all relationships, thereby making men in particular dependent on the good will of their wives (and of the magistrates who will judge the cases).
So in liberal France men do not end up getting left alone. There is a sword hanging over their heads in their relationships, courtesy of a state which thinks it best to manage relationships through crime laws.