Humanism is a democratic and ethical life stance, which affirms that human beings have the right and responsibility to give meaning and shape to their own lives. It stands for the building of a more humane society through an ethic based on human and other natural values in the spirit of reason and free inquiry through human capabilities. It is not theistic, and it does not accept supernatural views of reality (IHEU Minimum Statement on Humanism).
Humanism is foundational to our view of reality and our respect for science. Its modern incarnation began in the early 20th Century with John H. Dietrich, Charles Francis Potter, Raymond B. Bragg, and Roy Wood Sellars. They helped created the Humanist Manifesto I, which I still think is the best of the Manifestos in expressing the need for a new religion.
But Humanism has deep roots in the ancient world as well. For example, in China as Confucianism, in Greece as Epicureanism, in India in Charvaka, and in modern Existentialism.
My favorite book on “Humanistic Religious Naturalism” is Reason and Reverence by William R. Murry. A good background to the humanist Manifesto I is The Genesis of a Humanist Manifesto by Edwin H. Wilson. For a more secular take, see The Philosophy of Humanism by Corliss Lamont and Living Without Religion by Paul Kurtz.
Since I mentioned Paul Kurtz, I think he is probably one of the most underrated philosophers of our time. I really wish eupraxsophy, a term he coined, would have caught on. Bodhidaoism is a eupraxsophy, which means “good practical wisdom.”