Attempting to answer the question "what is a variable?," menger discusses the following topics: (1) numerical variables and variables in the sense of the logicians, (2) variable quantities, (3) scientific variable quantities, (4) functions, And (5) variable quantities and functions in pure and applied analysis. (staff).

One does not only talk about the length in inches of this sheet of paper but also about the length of this sheet, about length in inches and about length. A clarification of these and related concepts results from a combination of the theory of the length in a definite unit as a fluent, developed by one of the authors, with the other's concept of 2-place fluents. The length ratio L is defined by pairing a number L (α,β) to any (...) two objects of a certain kind, α,β (in a definite order). L thus may be described as the class of all pairs (α,β), L (α,β) for any objects α,β of the said kind. Length of this sheet and length in inches are specializations of this 2-place fluent. (shrink)

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