Abstract

This work presents both types of rationality proposed by Marcelo Dascal and analyses how they interact and complement each other. What is traditionally understood as scientific rationality is what Dascal refers to as hard rationality. Argumentation based on this form of rationality seeks the certainty, the conclusive proof. However, the philosopher broadens the concept of rationality, allowing the existence of a soft rationality, which deals in the area of opinions. Arguments built from this form of rationality seek the persuasion. Usually, Mathematics is taken as an example of hard rationality, since it is structured upon the demonstrative reasoning. Here, I show that mathematical demonstrations follow the deductive logic, deal with universals and seek proof, certainty. Thus, it is an example of hard rationality. However, when applied to particulars, it is possible to construct mathematical arguments to persuade, or highlight elements that support decision making, without determining which position is correct. These arguments are examples of soft rationality. Therefore, I want to demonstrate that both rationalities interact, and arguments build based on demonstrative logic can be used in argumentations that seek to convince.