ArgLab • Colloquium

Vasco Correia

Argumentation, rationality and reasonableness

Normative theories of argumentation often appeal to the notions of “reasonableness” and “rationality” to account for the requirement that arguers should comply with argumentation rules. As Van Eemeren and Grootendorst (2004, p. 123) point out, however, “it is often unclear exactly what [these words] are supposed to mean, and even if it is clear, the meaning is not always consistent”. Unlike most argumentation theorists, Van Eemeren and Grootendorst provide a clear distinction between the “rational” and the “reasonable” and develop what they call the “critical rationalist” approach to reasonableness, partly directed against Justificationism. One of the implications of this account, the authors suggest, is that “rationality is a necessary condition of reasonableness, but not automatically a sufficient one” (id., p. 125). In this paper I challenge the later assumption and argue that rationality is not a necessary condition of reasonableness (neither is reasonableness a necessary condition of rationality). This calls for a broader definition of both notions capable of taking into account cases of irrationality in which the arguers’ reasonableness is not necessarily undermined, and conversely cases of unreasonableness in which arguers remain fully rational. My suggestion is that John Rawls’ distinction between reasonableness and rationality is more fruitful in that respect and sheds a new light on the debate between Justificationists and critical rationalists.


Vasco Correia, Universidade Nova de Lisboa