Classifiers and decision makers.

The main objective of this paper is to point out the key relevance of the classification issue in mathematical modeling. In particular, it is stressed that standard logical structures are quite simple classification structures, where the allowed degrees of truth or falsehood are connected according to a linear ordering. But when viewed as a classification problem, much more complex logical structures appear in a natural way, showing in fact that the standard linear assumption was kind of artificial. Moreover, once we focus our attention on the classification problem we realize that a relevant portion of classical research devotes to decision making, therefore imposing some misleading restrictions: the true scientific issue is much more related to classification rather than to decision making.