Arguments from plausibility, in which an appeal is made to customary behavior, are often used in the legal practice. For example: Joran van derSloot must have murdered Natalee Holloway, otherwise he would have called an ambulance when she looked dead. As in the example, such arguments are often presented with an explicit appeal to an inference license that gives the argument amodus tollensstructure [if he had not murdered her...]. I will address the question what motivates such a presentation.