Abstract: The principle of proportionality is globally influential, yet its underlying conception is often misunderstood. Prevailing scholarship interprets it through a 'conception of limitation', viewing it merely as a restriction on either public power or fundamental rights. This paper argues that such a view is internally inconsistent and fails to capture the principle's essence. Instead, this paper proposes a 'conception of balance' rooted in the ethical doctrine of double effect. From this perspective, proportionality serves to optimally balance conflicts between fundamental rights and public interests, producing a dual rather than a singular restrictive effect. This interpretation not only offers a more coherent theoretical framework, distinct from cost-benefit analysis, but also provides a flexible ethical foundation that facilitates the principle's universalization and localization.