Barber paradox (Wikipedia)

an alternate form of

Russell’s paradox (Wikipedia) In mathematical logic, Russell’s paradox (also known as Russell’s antinomy) is a set-theoretic paradox published by the British philosopher and mathematician Bertrand Russell in 1901. Russell’s paradox shows that every set theory that contains an unrestricted comprehension principle leads to contradictions. The paradox had already been discovered independently in 1899 by the German mathematician Ernst Zermelo. However, Zermelo did not publish the idea, which remained known only to David Hilbert, Edmund Husserl, and other academics at the University of Göttingen. At the end of the 1890s, Georg Cantor – considered the founder of modern set theory – had already realized that his theory would lead to a contradiction, as he told Hilbert and Richard Dedekind by letter.

The barber paradox is a puzzle derived from Russell’s paradox. It was used by Bertrand Russell as an illustration of the paradox, though he attributes it to an unnamed person who suggested it to him. The puzzle shows that an apparently plausible scenario is logically impossible. Specifically, it describes a barber who is defined such that he both shaves himself and does not shave himself, which implies that no such barber exists.

Seattle Neighborhoods: University District — Thumbnail History (historylink.org) Seattle’s University District, home of the University of Washington since 1895, is located in the northeast section of the city, north of the Portage Bay part of Lake Union. Its main spurs to development were the developer James Moore (1861-1929), the 1895 move of the Territorial University from downtown to what was then called Brooklyn, and the Alaska-Yukon-Pacific Exposition on the University of Washington campus in 1909. In the late twentieth century, the main challenges to this “city within a city” have been the development of nearby malls. It is a neighborhood of restaurants, cafes, a renowned street fair, a farmer’s market, and a few venerable institutions such as the University Book Store, University Inn, and the Meany Hotel.

Bertrand Russell (Wikipedia) Bertrand Arthur William Russell, 3rd Earl Russell, OM, FRS (18 May 1872 – 2 February 1970) was a British mathematician, philosopher, logician, and public intellectual. He had a considerable influence on mathematics, logic, set theory, linguistics, artificial intelligence, cognitive science, computer science and various areas of analytic philosophy, especially philosophy of mathematics, philosophy of language, epistemology, and metaphysics.