Skip to main content
1 of 6
Paul Taylor
  • 8.5k
  • 1
  • 29
  • 58

Who first defined well-foundedness intuitionistically as the induction scheme?

Who was the first to state the definition of well-foundedness intuitionistically as the induction scheme?

$$ \forall \phi.\quad\frac{\forall x.(\forall y. y\prec x\Rightarrow \phi y)\Rightarrow \phi x}{\forall x.\phi x} $$

While I'm here, are the following historically correct?

  • Euclid's Elements Book VII Proposition 31 (the Euclidean algorithm for prime factorisation) says that an infinite descending sequence is impossible amongst the natural numbers.

  • What other forms of induction and recursion were stated before the 17th century?

  • Fermat, Pascal and Wallace in the 1650s stated induction in the form of the base case and induction step.

  • Cantor 1897 (earlier?) proved that, for any two well ordered sets, one is uniquely equivalent to an initial segment of the other.

  • Mirimanoff 1917 was the first to recognise the importance of the absence of infinite descending sequences in the consistency of set theory.

  • von Neumann 1925 proposed the first version of the axiom of foundation, that the system of set theory is the minimal one.

  • Zermelo 1930 first asserted the asiom foundation as the lack of infinite descending sequence of elements.

  • Zermelo 1935 was the first to study well-foundedness in the abstract, as atool forproof theory.

  • von Neumann 1928 was the first to prove the recursion theorem for ordinals.

I am currently working on the categorical reformulation of von Neumann's recursion theorem, for well founded coalgebras: http://www.paultaylor.eu/ordinals This includes the full bibliographical details of the above references.

I can read French and Italian reasonably fluently, but unfortunately not German.

Paul Taylor
  • 8.5k
  • 1
  • 29
  • 58