How did Darwin affect the religious lives of this first generation of thinkers to absorb him?

Peirce was an Episcopalian, and a believer. He believed that God's love was what gave evolution its form, what made it work. He didn't think that chance variation was enough of an explanation.

For James, Pragmatism was a reason for believing in God. He wanted to say it was okay to believe in God, even if you couldn't prove God existed. The prejudice of this scientific age was that if you couldn't prove it you had to treat belief in God as some sort of speculation, or metaphysics. James thought that if you believe God exists and it made a difference to you, then God exists and that belief is true.

So he defended religious faith and thought the religious instinct was very important in people's lives. A lot of his thought centers around the notion that there are certain circumstances people find themselves in where the only thing that can really save them is faith. There were some problems -most famously the problem of evil-that faith was the only legitimate way to deal with it.

You say James thought that " if you believe God exists and it made a difference to you, then God exists." As a religious stance, that sounds kind of cynical.

These days that sounds like a therapeutic thing to say, like something you'd hear Oprah Winfrey might say. But in 1900, the idea that you can choose to believe in something and it can be right for you was very radical. If you think about Hegel or Marx or even Darwin himself and the religious establishment, all the emphasis was on how little will the individual has, how life is determined by material or historical or providential force.

So when James and Dewey come along, and say, "No, you get a vote. You can make a difference by choosing one or the other of the beliefs that are presented to you." And that belief is a vote, and it will change the way the universe is.

In 1900, that's very liberating. No other philosophy was available that said you can change the way things are. The whole laissez faire economic and social philosophy told them that everything was predetermined, that market forces would determine how things would turn out all the time and to interfere with that was to interfere with nature. James and Dewey changed all that. Now I think has swung to the other extreme and it's sort of a piety that you can make a difference.Science so dominates now that the idea of a theological explanation of nature seems benighted to us. It's refreshing in a way to see the situation reversed on the great question of the 19th century. It was scientists who tended to justify slavery whereas the abolitionists were devout Christians.

Creationist theories suggested there was a hierarchy among races, or many of them did. That was why there was a tendency not to regard slavery as an evil. There was a feeling that white people were created to be superior. But the Bible itself doesn't make that distinction. It's a monogenous text: it tells a story of creation from an original pair. It's very like Darwin in that sense.