Argumentation theory underwent a significant development in the Fifties: its revival is usually connected to Perelman's criticism of formal logic and the development of informal logic. Interestingly enough, it was during this period that Artificial Intelligence (AI) was developed, and the following thesis (from now on referred to as the AI-thesis) defended: human reasoning can be emulated by machines. The paper investigates the relation between these two trends: is it possible to interpret the opposition between formal and informal logic as a move against the AI-thesis, and in particular against a premise of an argument that supports it? A distinction between a narrow and a broad notion of algorithm is discussed and evaluated with respect to the possibility of rephrasing the AIthesis as a foundational problem for argumentation theory.