No, not third world. Third world (Dritte Welt, tiers monde) dates back to the French demographer Alfred Sauvy’s (Eng., Ger.) article from 1952 in L’Observateur “Trois mondes, une planete”. He describes and categorizes circa 130 states as economically underdeveloped in comparison to the “First” and “Second” world, that could roughly be equaled with “The West” and “The East” – remember we are right in the Cold War at the beginning fifties. Later the “blockfree states” (Ger., Eng.) led by Egypt (Nasser), India (Nehru), Indonesia (Sukarno) and Jugoslawia (Tito) referred to themselves sometimes as “third world”, but this use of the phrase did not really get accepted.
“Welt 3” refers to the “Drei Welten Lehre” * von Sir Karl Popper (Eng., Ger.). Sir Karl may best be remembered for his thoughts about science itself (Wissenschaftstheorie: Falsifikationismus (Ger., Eng.), society (Gesellschaftstheorie) as given in his book “Offene Gesellschaft” (Ger., Eng.) and his role in the “Positivismusstreit” (Ger., Eng.). He is seen as founding figure of a philosophical direction called Kritischer Rationalismus (Ger., Eng.).
A science consists always of its own history – and strangely enough in this “cultural science” called Volkskunde no reception of the great thinkers ideas took place since they were first formulated in the end-sixties. To my eternal shame I have to confess that I covered Popper in my seminar only regarding the “open society” and the “Positivismusstreit”, in the shady and lawless border areas to sociology – sociologists, what do they know?
M. Scharfe is the first who attempts to use Popper’s thoughts in his outstanding book “Menschenwerk”, to what I was referring here.
I am too tired to explain “Welt 3” now, it will follow suit.
P.s. Here‘s the Stanford article about Popper.
* This “article” is a stub. But gives an interesting link leading to Popper’s lecture given 1978 about the “Three worlds” in Michigan (pdf, 27 pages).