There’s a lot of ground to cover concerning the manifestos and one really isn’t going to find a whole lot about them outside of humanist and Unitarian Universalists websites, except maybe Fundamngelical propaganda. That said, I do have a lot of humanist links to give humanist books to share.
That said, after the first manifesto, a second one came along in the 70s. Paul Kurtz and Edwin H. Wilson nailed out a new one in 1973. Why? Because the Humanist Manifesto is one that grows and changes as time passes. It was meant to evolve as society and the world changed over time.
This is the manifesto that I think Gene Roddenberry (link to AHA interview) spent most of his life adhering to, not to the letter like a religion, but as a guide, maybe even a reminder. I also think it is one that the retired Bishop Spong and other religious humanists or humanistic Xians adhere to, but not necessarily the U.U. They to have a more modern version on their site or at least some of their sites, but that’s not to say they don’t follow the AHA’s version. UU ministers have notorious for signing the various Humanist Manifestos.
When I was a teen I read about Humanism and years later I found the manifesto very familiar. Sadly, while I was reading the humanist info (it was probably the AHA interview with Gene Roddenberry), my mother walked into my room without knocking, yanked it out of my hand, shouted, “This is not Christian”, and walked out of the room with it. I never saw it again.
I do want to make note right now, that there was another Anglican priest who tried support humanistic values into Xianity. Anthony Freeman wrote the book “God In Us: A Case for Christian Humanism”. He was excommunicated for it, but he basically wrote Bishop Spong has said for years. The forward in the updated edition was written by Bishop John Shelby Spong. That’s not to say Freeman didn’t impress some Episcopalians and Anglicans. Sites like SOF (Sea of Faith) in Australia and the U.K. popped up. That said, they are a bit too religious for me, but they are examples of Humanistic Christianity. Don Cupitt, another Anglican minister, though I think he left the Church, also wrote “Radical Theology”. All three former ministers helped to start SOF and Bishop Spong started a similar group in the U.S., but I forgot what it was called. I still think they are more religious than humanist, but that said, they are humanistic.
There is also humanistic Judaism, as I mentioned before and others. Some of these groups also signed the second manifestor too. This group also claims Greg Epstein as a Humanist Jew, but he calls himself a humanist. Either way, I accept him as a humanist and a humanist minister. Sherwin T Wine is also claimed as a Jew and a humanist and I do believe it is possible to be both.
Now we also have humanist groups around the U.S. - Houston and KC, as well as the various U.U.s and also Ethical Societies around the U.S., which are all humanist groups.
During the 70s, about the only organizations for non-theists were the AHA, American Atheists, UUs, and Ethical Societies, but that was about it. Today, we can find various humanists and atheists groups and organizations all over the U.S.
This leads us to the third humanist manifesto in 2003 AND The Humanist Manifesto 2000, by Paul Kurtz. Now why are there two, you may ask? This is about the time Paul Kurtz left the AHA and created the Secular Humanist. This isn’t discussed much due to not wanting to discuss disagreements among humanists, for whatever reason.
That said, most notably we have humanists and UU ministers, as well as others, signing all the manifestos with the AHA. Some religious clergy signed the first and the second manifestos, but you don’t see religious clergy with the third one. I missed this one, written by Paul Kurtz in 1980. I don’t know when he wrote the Affirmations, but anyone can read those too. Sadly, the only article I can find on the 2000 one by Paul Kurtz is for subscribers only, but it can be read here, if you have a subscription: https://secularhumanism.org/1999/10/humanist-menifesto-2000/
Keep in mind, humanism is not a religion. I consider it a way of life, much like the Roddenberrys do and did. That said, you can read more on the AHA site or at Free Inquiry (a link to a page on Free Inquiry site above), and here on CFI. Edd Doerr and Fred Edwords, both on AHA site, wrote a lot about humanism also.
There is so much more to discuss about humanism, but the manifestos are a good starting point, IMO. You can learn more at Humanists International, Institute for Humanist Studies, AHA Center for Education, and others. There was a The Continuum of Humanist Education (COHE), where I took courses in humanism and it’s how I got Fowler’s book, because she created some of the courses there, but it seems defunct now (the site won’t load) and you really don’t have to take courses to learn about humanism. There are plenty of books on humanism, some I have listed. Paul Kurtz wrote a lot, as well as Edd Doerr and Fred Edwords (we’ve lost all three now, I think). There is also The Philosophy of Humanism, by Corliss Lamont. I bought the book after I saw the PDF. He also wrote The Affirmative Ethics of Humanism, too.
I probably threw an awful lot, just on the manifestos alone, which seems like also involves a lot of info on humanism too. I’ll stop and allow people to go over what all I posted and comment on what they can. I have a lot more on humanism too, but this is a good start to encourage discussion at least on the manifestos.