Why is 1 + 1 = 2?

Wuu Yang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Too often we take the method of decimal addition to be the definition of addition. We clarify this misunderstanding by first giving a definition of addition and then proving that the decimal addition method is both sound and complete with respect to the given definition. By showing the soundness and completeness of decimal addition with respect to the addition of natural numbers, we actually propose a new approach to algorithm correctness. We also discuss the differences between our logic approach and the traditional axiomatic approach.

Original languageEnglish
Pages (from-to)425-443
Number of pages19
JournalJournal of Information Science and Engineering
Issue number3
StatePublished - 1 May 2002


  • Addition
  • Algorithm correctness
  • Arithmetic
  • Decimal addition
  • Decimal notation
  • Foundation of mathematics
  • Logic

Fingerprint Dive into the research topics of 'Why is 1 + 1 = 2?'. Together they form a unique fingerprint.

Cite this