Mathematical definition of number?

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Discussion Overview

The discussion revolves around the mathematical definition of "number," exploring its implications, inclusions, and exclusions within various mathematical structures. Participants examine the nature of numbers in relation to sets, structures, and undefined terms in mathematics, with a focus on theoretical and conceptual aspects.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants question whether "number" should be defined as a member of a mathematical structure, noting that this could include functions and vectors, which may not align with common intuitions about numbers.
  • Others propose that "number" could be defined as a member of a magma, but this would exclude complex numbers, raising concerns about the adequacy of such definitions.
  • There is a suggestion that the term "number" is too vague and that it might be better to refer to "elements of specific sets or structures" instead.
  • Several participants highlight the ambiguity in what constitutes a "number," questioning whether real numbers, complex numbers, p-adic numbers, or even infinity should be included.
  • Some argue that undefined terms are essential in mathematics, and that "number" can serve as shorthand for various types of mathematical objects depending on context.
  • There is a discussion about whether numbers are axiomatized from sets or vice versa, and whether structures arise from elements or elements from structures.
  • One viewpoint suggests that numbers are constructs of human experience, while another argues that sets may be more fundamental than numbers in terms of mathematical operations.
  • Some participants assert that "number" is an axiom, existing due to repeated human experience, while others clarify that "numbers exist" is a statement that can be proven through reference.
  • There is a contention regarding the definition of rational numbers, with some arguing that they should include negative numbers, while others defend a more restrictive definition based on counting numbers.
  • Participants discuss the possibility of defining numbers through either a constructivist or axiomatic approach, noting that both methods can yield isomorphic sets.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the definition and nature of "number," with no consensus reached on a singular definition or framework. The discussion remains unresolved, highlighting the complexity and ambiguity surrounding the term.

Contextual Notes

Limitations include the lack of clarity on foundational definitions, the dependence on context for understanding what constitutes a number, and unresolved questions about the relationship between numbers and sets.

  • #31
Yes, because you can't define "cardinality" until after you have the natural numbers.
 

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