 It was only when looking back on his work, in the programmatic 1924 essay “Logical Atomism”, that Russell first described various logical definitions and philosophical analyses as “logical constructions”. He listed as examples the Frege-Russell definition of numbers as classes, the theory of definite descriptions, the construction of matter from sense data and then series, ordinal numbers and real numbers. Because of the particular nature of Russell’s use of “contextual” definitions of expressions for classes, and the distinctive character of the theory of definite descriptions, he regularly called the expressions for such entities “incomplete symbols” and the entities themselves “logical fictions”.