[betty boop]

"The recent irruption of atheism can be traced to the Darwinian creed...."

I’d have to question its usage in this context.

The context is social change within the timeframe you suggest (150 years). I don't think the usage is at all hyperbolic. People bragging about their atheism seems to be a rather striking development. Dawkins' and Dennett's "brights" campaign is a good illustration of an "irruption of atheism" that is quite aggressive in its tactics.

At least it looks that way to me, FWIW.

[js1138]

Dawkins' and Dennett's "brights" campaign is a good illustration of an "irruption of atheism" that is quite aggressive in its tactics.

I'm somewhat at a loss as to how writing books can be construed as "aggressive."