However, this confidence was shattered when in 1902 the British logician and philosopher Bertrand Russell produced his now famous paradox (itself anticipated by Cantor, and a direct descendant of Cantor’s ‘diagonal slash’ argument). To understand Russell’s argument, we first need some feeling for what is involved in considering sets as completed wholes. We may imagine some set that is characterized in terms of a particular property. For example, the set of red things is characterized in terms of the property of redness: something belongs to that set if and only if it has redness. This allows
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