In this paper, the defeasible argumentation scheme for practical reasoning (Walton 1990) is revised. To replace the old scheme, two new schemes are presented, each with a matching set of critical questions. One is a purely instrumental scheme, while the other is a more complex scheme that takes values into account. It is argued that a given instance of practical reasoning can be evaluated, using schemes and sets of critical questions, in three ways: by attacking one or more premises of the argument, by attacking the inferential link between the premises and conclusion, or by mounting a counter-argument. It is argued that such an evaluation can be carried out in many cases using an argument diagram structure in which all components of the practical reasoning in the case are represented as premises, conclusions, and inferential links between them that can be labeled as argumentation schemes. This system works if every critical question can be classified as a assumption of or an exception to the original argument. However, it is also argued that this system does not work in all cases, namely those where epistemic closure is problematic because of intractable disputes about burden of proof.
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