  This paper rests to a large extend on a paper I wrote some time ago on
'Duality in generalized Ising models and phase transitions without local order
parameter'. It deals with Ising models with interactions containing products of
more than two spins. In contrast to the old paper I will first give examples
before I come to the general statements. Of particular interest is a gauge
invariant Ising model in four dimensions. It has important properties in common
with models for quantum chromodynamics as developed by Ken Wilson. One phase
yields an area law for the Wilson-loop yielding an interaction increasing
proportional to the distance and thus corresponding to quark-confinement. The
other phase yields a perimeter law allowing for a quark-gluon plasma.
