Some human formal thought processes are completely determinate in their conceptual content (e.g., pure mathematics or the absolute Law of Non-Contradiction).
No purely material structure or process can ever be inherently determinate, because matter is always fundamentally open to multiple algorithmic interpretations (indeterminate).
Therefore, those determinate human formal thought processes cannot be purely material structures or processes.
Syllogism for Aquinas's First Way
Modern Rendition by Edward Feser.
Change is a real, mind-independent feature of the physical universe.
Change is precisely defined as the reduction of a thing's potentiality to a state of actuality (e.g., cold water possessing the potential to become hot water).
No potential can actualize itself, because a potential does not yet exist physically; therefore, any potential being actualized requires something already actual to actualize it (the Principle of Causality).
The continuous change and operation of any composite substance at any given moment presuppose a concurrent, simultaneous hierarchy of active actualizers (an essentially ordered/hierarchical causal series).
A hierarchical causal series cannot regress infinitely, because the secondary members have no causal power of their own and merely transmit power; an infinite regress of instrumental causes without a source is a logical absurdity (like a mirror reflecting a light that does not exist).
Therefore, there must exist an absolutely primary actualizer that initiates and sustains the causal series without being actualized by anything else.
This primary actualizer must be Pure Actuality (Actus Purus), completely devoid of any passive potency, meaning it is necessarily unchanging, atemporal, immaterial, and the continuous Sustainer of all being.
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An Introduction to Catholic Philosophy for the Modern Family.