Humanists International is not a body one joins. It is a federation of organisations, around a hundred and twenty of them, in more than sixty countries, with no individual membership, which means that any figure purporting to give the number of humanists in the world is not one it produces or could produce.
It was founded at Amsterdam in 1952 as the International Humanist and Ethical Union, bringing together five existing national humanist and ethical groups, with Julian Huxley, the Dutch philosopher Jaap van Praag and the British humanist Harold Blackham as its principal figures. Van Praag was its first chair. It took its present name in 2019.
Its statement of principles is the Amsterdam Declaration, adopted at that founding congress, revised in 2002, and revised again in 2022 for the federation's seventieth anniversary. It is the nearest thing organised humanism has to a creed, and it is written with visible care not to be one: it sets out humanism as ethical, rational, democratic and non-theistic, insists that it is a life stance rather than a dogma, and commits to the free expression of dissent from itself.
The revisions are informative in their own right. A movement that rewrites its founding statement every twenty years is either unstable or serious about the claim that convictions should follow evidence, and the substance of the changes suggests the second.
Its member bodies range from national organisations with parliamentary influence to small groups operating in places where being openly non-religious is dangerous, and the federation's work reflects both ends of that range.