INTRODUCTION

Kanon (euklees kai semnos) and kriterion were kingly words which lived and reigned for four hundred years in the philosophy of the hellenistic period. For they answered the questions: is there objective truth? How can it be known? To Stoics and Epicureans, who gave an affirmative answer to the first question, the answer to the second question was ‘by following the criterion or canon’. For the Sceptics who denied truth, its proposed canon was the target of their attack. Regula (kanon) also had a common legal application as a summary principle which governed any situation within a certain definition, but Cicero is the chief Latin source. Since Tertullian has commonly been regarded as more of a lawyer than he was, the legal definition has seemed more useful than the philosophical; this is not the case and we shall find a strong philosophical interest in the Christian use of this concept.

The rule of truth or faith is central to the emergence of orthodoxy. It has been regarded either as restrictive to the use of reason (Celsus made it central in his attack) or (by nineteenth-century liberals) as the decline into intellectualism which reduced a gospel to a set of doctrines. In the hands of Tertullian it begins as a barrier to enquiry. Arguing about scripture is useless and uncertain; only the rule is decisive and apostolic. The rule is enough; after Christ there is no place for argument (De praescriptione hereticorum, hereafter Praescr., (7).