 In our example \(\{a,d\}\) and \(\{b,d\}\) are the two preferred sets. This shows that the preferred semantics does not determine a unique selection. In order to define a consequence relation we can proceed either according to the credulous rationale or according to the skeptical rationale. Considering an abstract argumentation framework based on \(\Gamma\), SRules, and DRules, we give two examples of how a consequence set can be characterized by means of the skeptical approach  (Prakken 2010):  