Reason-based Logic: a logic for reasoning with rules and reasons

The main claim of this paper is that reasoning with rules, especially rules of law, is different from reasoning with statements that are true or false. This difference is, amongst others, reflected in the defeasibility of arguments in which rules play a role. Reason-Based Logic is a logic that has special facilities for dealing with rules and with reasons based on rules. In particular it allows arguments in which conclusions are derived by 'weighing ' the reasons that plead for and against them. In this article we illustrate some characteristics of reasoning with rules, and show how Reason-Based Logic deals with these characteristics. The article is concluded with some general considerations concerning Reason-Based Logic, and a comparison with some other logics for defeasible reasoning. Rules are different from statements, and a logic that deals with rules should take this difference seriously. This is maybe the most important message that this article contains. The rest might be considered as a mere elaboration of this claim. We will validate this claim and show its implications. In this introduction we focus on the application of rules to illustrate th