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Written in first order logic, Hatcher's proof of God is based on three axioms that he calls "empirically grounded" and an apriori assumption that "something exists."
The axioms are that:
P1. The principle of sufficient reason: All phenomena are either self-caused (i.e. A->A) or other-caused (B->A; B is not equal to A) but not both. Put another way, this principle says that the question "why?" is always meaningful. Everything happens for a reason.
P2. The potency principle: If A -> B then for all C element of B, A -> C. In other words if A is the cause of B then A is the cause of every part of B. There are several notions of causality in philosophy. Hatcher's notion of causality is total causality; i.e. it is not the straw that breaks the camel's back but the 1000 straws before it, the camel, gravity, and so forth, that give rise to the camel breaking its back.
P3. The principle of limitation: For all A, where A is an element of B, B -> A does not hold. This says a system (which Hatcher represents as a set) cannot be the cause of its own components. Hatcher justifies this by explaining any system has (1) form (the parts) and (2) function (the relationship between the parts). A car (the system) cannot be the cause of its own steering wheel (a part), because the car does not even logically exist until the steering wheel exists. Thus the car's existence cannot precede the steering wheel's existence.
Hatcher shows that the logical outcome of these 3 axioms together with the above noted assumption are the existence of a "unique, universal, uncaused cause."