Function theory assumes that the universe contains ‘things’ that are subject to change. Experience tells us that the changes in one thing can cause change in one or more other things. When a variable in a first thing is related to one or more variables in some other thing, the other thing is said to be a ‘function’ of the variable found in the first thing. The first variable is called the ‘independent’ variable whereas the one or more variables are called the ‘dependent’ variable(s).
Since all variables represent all changes found in all things in the universe, one must seek a thing that is the origin of all variables. This thing will not be found in the unchanging constants discussed above. But, it can be found if all variables and all constants in the universe are originated by a thing that creates all things. As seen, the independent variables and dependent variables of the universe would not exist without God.
Function theory is one of the most powerful tools that mathematicians found. But, they wrongly limited it to a finite world. By adding this limit to function theory, they rejected God. With respect to function theory, God is the Function of all functions. But, God is also the Truth of all truths; the Maximum of all maximums; the Contradiction of all contradictions; etc.
On the subjects --- universe, things, and function theory, all sciences can be questioned. These important fields of thought seem to be drifting.