Is there a ‘central principle’ of Calvinism? This article explores this question mainly from the
viewpoint of reformational philosophy. It does so firstly by introducing criteria that should
be used to identify, if possible, such a central ‘organon’ of Calvinism. Then a few proposals are
evaluated, and their strong and weak points are discussed. The most credible candidate for the
role of central principle is argued to be an ‘idea of law’ rooted in the biblical groundmotif and
traditionally defined as ‘sphere-sovereignty’. More recent characterisations of this cosmonomic
idea are considered. A few objections and alternative proposals are also discussed. The article
is concluded with a few questions, calling for further research on the topic.