English summary: Christoph Markschies shows that ancient Christian theology must always be seen with a view to its specifically institutional context. Thus the canon of biblical writings is not only of varying length in the works of the apocalyptists, free teachers, in the school of Origen or in the various liturgies, it also has different functions. The author begins with a description of these various institutions and then uses the biblical canon to explain those characteristics of a theological concept which unite and those which differ. The book is built around studies of the idea of theology and an application of the answers to the age-old question related to the unity and plurality of ancient Christianity. German description: Christoph Markschies zeigt, dass die antike christliche Theologie stets mit Blick auf ihren spezifischen institutionellen Kontext verstanden werden muss: So hatte beispielsweise der Kanon biblischer Schriften bei Apokalyptikern, freien Lehrern, in der Schule des Origenes oder in den verschiedenen Liturgien nicht nur einen unterschiedlichen Umfang, sondern auch eine unterschiedliche Funktion.