MARCO ANTONIO ANTONELLI GAIARSA

Decision Theory is a field that studies decision making processes. Is this work, our emphasis is in the normative theory of rational decision. This means that our goal is to investigate the decision making processes that satisfy rationality criteria explored via abstract considerations. The focus is to point out the adequate decision process of an individual that wants to follow rationality norms. We use references from Logic, Philosophy, Economy and Mathematics to investigate intuitions about rationality, seeking consequences of those in formal investigations and using explicit methodologies to indicate restrictions on the individual for the sake of rationality. We use a minimal demand approach, meaning that we want our decision maker to only be restricted when we show, with complete formal and mathematical clarity, that he may be harmed in not following the restriction. We try, when possible, to keep real decision makers in sight, considering incomplete information and limited capacities, avoiding logically valid tools that involve infinite elements, such as sets and rules, if we have reasons to believe that they are not viable to the most relevant decision makers, such as individuals and organizations. This work is split into three chapters. The first introduces the fundamental definitions of the field, as well as considerations of the most important elements of the area. In this first chapter, we introduce the notions of belief and preference, pointing out the complexity of these topics. The second chapter examines more deeply the notion of belief. with the classical solutions and considerations on limitations and alternatives. The third chapter does the same, with the notion of preference.