Naess's Dichotomy of Tenability and Relevance

In his Communication and Argument Arne Naess discusses how to evaluate reasons advanced to support (and objections advanced to detract from) a given point of view. 1 According to Naess there are two distinct issues to be settled with respect to each separate reason: the issue of its tenability and the issue of its relevance. The distinction itself is, I think, booth tenable and relevant. However its application is not as straightforward as one might at first suppose. I shall in turn discuss some difficulties and possibilities of applying the distinction in contexts of: 1. evaluation 2. the production and recognition of higher order reas ons and objections 3. formal discussion