Chapter 4 The Decision: Methods

In Chapter 3, we took the time to discover the current of MCDA (Multi-Criteria Decision-Aiding, see section 2.5) and its approach for characterizing the decision problem as well as its essential notions, i.e. preference, on the one hand, and order, on the other hand. It was therefore possible for us to show that the different types of preference considered only allowed the development of pre-orders, which could not systematize the choice and therefore the decision. Through the central stage of the decision process, this chapter will address the methods proposed in MCDA, what and how they bring the “extra” needed to come closer to order, which enables choice. Coming closer, yes, to greater or lesser degrees, but coming closer only. Deducing a total order would rely, in this formalism, on the principle of stating a number of hypotheses, which cannot be coherent with the vision that MCDA has of decisions and the decision-makers’ involvement in the process. Moreover, although the basic idea is still choosing from a comparison (so from an order), an additional principle is specified, that of “synthesis”. This synthesis or even combination or aggregation has the aim of bringing together “information on different viewpoints or aspects concerning a set of objects (or alternatives, actions), and choosing one or more objects from among this set” [GRA 05a].