<p>This paper aims to demonstrate how a rigorous definition of determinism can be formulated and applied to a formal axiomatization of a physical theory. Examining an example of Newtonian classical particle mechanics (CPM) formalized in set-theoretical axioms by Patrick Suppes, the paper shows why definitions of determinism based on the temporal development of physical systems—such as those proposed by Suppes (2002) and Montague (1974)—fail to assess determinism correctly. It is argued that, to deliver a meaningful verdict, the definition of determinism cannot be applied to the entire <i>framework</i> of CPM itself, but rather to its particular <i>theories</i>: definitions of specific physical systems that incorporate the force equation. Therefore, the verdict of determinism or indeterminism typically depends on the uniqueness (or non-uniqueness) of solutions to the differential equations governing the system’s behavior. The paper concludes with a demonstration of how a formally correct definition of determinism can be used to show the indeterminism of the theory of Norton’s dome stated within the framework of CPM. Although the example concerns pre-relativistic Newtonian mechanics, the crucial philosophical distinction between frameworks and theories extends beyond this case and suggests that assessing the determinism of any physical theory requires special caution to distinguish it properly from its framework.</p>