History of humanism

Philosophies grounded in human reason and experience rather than divine revelation can be traced back at least 2,500 years in China, India and Europe, and are found in many other cultures.

In the UK we are most familiar with the tradition of thought developed by the ancient Greeks and Romans which flowered again in the Renaissance and led to the Enlightenment and development of modern science. Greek philosophers like Democritus, Socrates and Cicero questioned conventional beliefs and explored how to live a good life. The Romans used the word ‘humanitas’ to mean both humane learning – ‘education in the liberal arts’ and philanthropy – ‘friendly spirit and good-feeling towards all men without distinction’.

Modern British humanism evolved specifically from the 19th and early 20th century ethical movement which wanted action to help the poor, end the exploitation of labour, see equal rights for women and other social reforms, and was influenced by Kantian ideas that you can’t prove the existence of god or afterlife and that morality can be independent of theology. “Deed not creed” was their phrase.

For a great introduction to humanist thought go to the BHA site.
The Wikipedia site also contains a lot of useful information on humanism.