Abstract

On standard accounts of practical reasoning, the reasoner, the valuer and the agent are the same person - as this description of a simple piece of reasoning can illustrate: "I want to stay dry. I believe I stay dry only if a carry an umbrella. Therefore I should carry an umbrella". But much of our practical reasoning is not of this kind. I call reasoning where the reasoner, the valuer and the agent are not identical "non-standard" reasoning. For example, "my" reasoning about "your" carrying an umbrella can be described as follows: "I think you want to stay dry. I believe you stay dry only if you carry an umbrella. Therefore you should carry an umbrella". The reasoner is here different from the valuer and the agent: The aim of this article was to assess the validity of non-standard reasoning. In order to achieve this, I have sketched (Section 1) when practical reasoning in general is valid. In Section 2 I have described the main forms of non-standard reasoning one by one and examine under what conditions, if any, they are logically valid.