The views concerning the Roman law concept of ius naturale basically come into two groups. Some authors accept the existence of ius naturale as practically binding law, whereas others regard it a pure philosophical Gedankenexperiment. This twofold state of ideas on ius naturale are fuelled for the most part by the contemporary Meinungsklima, though primary sources also raise some important issues of interpretation, increasing obscurity of this notion. It could therefore be set out to give a brief outline of the abstract approach and concept of ius naturale put forward by Ulpian at the beginning of the Digest.
A particularly interesting factor in close connection with this topic is the direct link made up between ius naturale and naturalis ratio, though this latter term is applied with regard to ius gentium. Consequently, in addition to considerations regarding ius naturale, it could likewise be worthwhile to try to point out how these two normative layers influence each other, and what consequences are drawn by secondary authors on this topic. When trying to collect the most common arguments and counter-arguments within this scope, a systematic understanding of both ius naturale and gentium is hopefully becoming eligible.