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Subject Philosophy

DOI: 10.1111/b.9781405106795.2004.x


L ogic A collection of entities satisfying a condition for membership in the class, that is, having certain common properties. The notion of a class or set is fundamental to set theory . A class is said to be open if it has infinite members and closed if its members are numerable. According to the axiom of extensionality, if two classes are exactly alike with respect to their members, they are identical. If a class has no members, it is called the null class or empty class. Class is usually used interchangeably with set, but some suggest that while set covers only those classes that are members of other classes, class covers collections that are not members of any other classes. The distinction is thought to be significant for solving Russell's paradox , which is also called the class paradox. “By ‘class’ I mean things that have members.” D. Lewis, Parts of Classes ... log in or subscribe to read full text

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