The Ubiquitous Axiom

Victor Pambuccian, Celia Schacht

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


This paper starts with a survey of what is known regarding an axiom, referred to as the Lotschnittaxiom, stating that the perpendiculars to the sides of a right angle intersect. Several statements are presented that turn out to rather unexpectedly be equivalent, with plane absolute geometry without the Archimedean axiom as a background, to the Lotschnittaxiom. One natural statement is shown to be strictly weaker than the Lotschnittaxiom, creating a chain of four statements, starting with the Euclidean parallel postulate, each weaker than the previous one. It then moves on to provide surprising equivalents, expressed as pure incidence statements, for both the Lotschnittaxiom and Aristotle’s axiom, whose conjunction is equivalent to the Euclidean parallel postulate. The new incidence-geometric axioms are shown to be syntactically simplest.

Original languageEnglish (US)
Article number114
JournalResults in Mathematics
Issue number3
StatePublished - Aug 2021


  • Aristotle’s axiom
  • Euclidean parallel postulate
  • Lotschnittaxiom
  • incidence geometry
  • plane absolute geometry

ASJC Scopus subject areas

  • Mathematics (miscellaneous)
  • Applied Mathematics


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