[ciphol]

> how can he pin down the demographic decline as caused by the Catholic Church’s decline ?

He gives several data points for secularization, such as the language people chose to use in their wills. Since there is a strong general correlation between low fertility and low religion, it seems likely that these are causally linked in 18th century France, rather than coincidentally happening at the same time.

It's a harder question why France in particular secularized at this time. The argument he very tentatively proposes is that freedom from religious coercion leads people to tend to become more religious (as can be seen by comparing the US to Europe over the last few centuries) and that France, due to its strong counter-reformation, had an unusually high level of religious coercion.

> Why wouldn’t it the other way round, with the core causes of the French decline also triggering less religiousness ?

What do you mean by "French decline"? Its loss of status as a superpower starting in 1815? That postdates the decline in religiousness.

[makeitdouble]

> Since there is a strong general correlation between low fertility and low religion

The article isn’t proving that point, and I’d argue other conditions, in particular mortality rates or living conditions in general have more of a widely accepted impact on fertility than religion.

I’d be open to see religion playing a role in this narrative, but IMHO it needs be more than an opinion or a hunch.

> “French decline"

I meant by that the decline in population