Simple axioms that are obviously true in $\mathbb{N}$
Tomasz Połacik, Wim Ruitenburg · Project Euclid (Cornell University) · 2003
We discuss simple subtheories of Peano arithmetic over languages which include the monus function. The system $\\mathrm{ZDL}$ corresponds with $\\mathrm{PA}^-$. The choice of language permits our theories to have special universal axiomatizations; their classes of models have corresponding model theoretic properties.