On Rational Decision with Subjective Probability in Design

Rationality has been regarded by many in the school of normative decision making as the sole criterion for good decisions. Its foundation is the subjective and personal interpretation of probability. In this brief, I argue that rational decision with personal probability is based on several assumptions and the validity of these assumptions is vastly debatable. First, I show that the history of the probability theory is the debate between interpretations of probability. The conclusion that subjective probability is the only interpretation will simply exclude the theory itself from applications in physical sciences such as engineering. Then, it is demonstrated that the assumptions of the Dutch book arguments, which are used as the philosophical base for rational or coherent decisions, are subject to debate. At the end, it is argued that the rational decision making based on the expected utility theory is purely on the coherent preference and nothing else. The further restriction on probability measures is a misinterpretation of the theory of preference. The view that rational design is equivalent to coherent design decisions is an oversimplification on real-world engineering issues.