Strict finitists identify the natural numbers with those representable as unary numerals constructible in practice.

This view is most prominently associated with Yessenin-Volpin (1961; 1970), who is in turn best known for questioning whether expressions such as \(10^{12}\) or \(2^{50}\) denote natural numbers. e. numbers up to which we may count in practice. On this basis, he outlined a foundational program wherein feasibility is treated as a basic notion and traditional arguments in favor of the validity of mathematical induction and the uniqueness of the natural number series are called into question. [48]