The aim of this article is to show that there are fundamental philosophical problems around informal logic, which philosophy of logic should pay attention to. This article is contrary to the idea that this discipline is only a “deductive formal logic applied to ordinary language, with didactic aims”. On the contrary, it is shown that informal logic’s subject matter is different from formal logic’s, because the former does not study inferences or reasoning but arguments, in short, their semantics, pragmatics, rhetorical and dialogue aspects. Finally, it explains that the main philosophical problem of informal logic, namely, if arguments could be formalized, is still open and there are two extreme positions about this problem: formalism and...