Human beings choose rationally according to their own belief systems. Wit-hout taking into consideration these belief systems, which do not only contain theoretical assumptions about reality but also practical convictions, emotions, evaluations and preferences, it is not possible to understand how and why they choose and decide as they choose and de-cide under uncertainty. Belief systems are of great utility for beings whose form of rationality is a limited and boun-ded one. Due to the qualitative structure of belief systems, the mathematical models develo-ped in the fields of game theory and rational choice theory are not al-ways the adequate instrument to conceptualize them.
