The Continuous Actualization Requirement: A Reconstruction of the Aristotelian–Thomistic Argument from Causation

The Aristotelian–Thomistic argument from change proceeds from the actualization of potential toward a first actualizer and, in its developed classical-theistic form, toward Pure Actuality. This paper reconstructs that reasoning while isolating a consequence that deserves explicit treatment: if Pure Actuality actualizes anything, its actualizing cannot be newly initiated. A transition from not actualizing to actualizing would introduce a previously unrealized actuality and would therefore be incompatible with Pure Actuality. This paper calls the resulting principle the Continuous Actualization Requirement. The requirement does not uniquely determine how Pure Actuality relates to dependent reality. Two models remain conceptually available. Continuous Actualization Model A — Foundational Sustaining Actualization — holds that Pure Actuality continuously or timelessly sustains a foundational reality through which secondary actualizations unfold. Continuous Actualization Model B — Universal Sustaining Actualization — holds that Pure Actuality continuously or timelessly sustains all dependent beings, powers, and actualizations. The paper argues neither that the Foundational Model is true nor that the Universal Model is false. Its narrower claim is that the core argument from causation does not, without additional premises, establish the Universal Model as the only interpretation of Pure Actuality. The result is an underdetermination challenge: the inference from Pure Actuality to the classical-theistic God requires more argument than the causal reconstruction alone provides.