What Is Fear? Redefining Anxiety and Accountability Through State-Space Expansion

This work proposes a structural reinterpretation of fear, anxiety, and distrust,not as purely emotional phenomena, but as consequences of uncertainty in action-relevant state spaces. Fear is defined as the volume of an uncertain state space, determined bythe number of variables involved in action selection and the range of values those variables may take. Under this framework, the paper explains within a single principle: why ambiguous situations feel more frightening than explicit danger, why expressionless faces, darkness, silence, and lack of explanation evoke fear, and why explanation and transparency reduce anxiety and distrust. Responsibility of explanation is redefined not as emotional reassurance,but as an act of state-space reduction. This paper integrates insights from psychology, evolutionary theory, information theory,and social theory, offering a unified conceptual framework for understanding fear and uncertainty.The model further provides practical implications for social systems, organizational management,user interface design, and explainable AI. This record includes both the original Japanese version and an English version that isstructurally equivalent. Both versions are released under the same DOI.