I've always been interested in Freudenthal's work, although I've never had the time to work through the book in detail. A second volume was planned but never fi

I've always been interested in Freudenthal's work, although I've never had the time to work through the book in detail. A second volume was planned but never finished. That's such a pity, because in that volume he planned to formalize interesting social concepts. Anyway, it's a must read for anyone interested in communication with aliens. I believe it would work, and his way of distinguishing between false and wrong is ingenious. The book is unfortunately hard to get, but there are digital copies around. Good reading if you don't shy away from some old-style Carnap-inspired logic notation.