A problem with how theists think.

[Esquilax]

I was assuming that there was some form of reasoning/basis  behind your "if you think about it", and asking you to explain how you came to this conclusion. 

For me, it's a matter of examining the surrounding arguments. So many theistic positions are predicated on the universe, or some subset of it, being "too X" to have arisen sans deity: the universe is too well designed to have arisen naturally, biology is too complex to have evolved, etc etc. To then turn around and posit an infinitely more complex entity as the solution to those problems is to discard the very contentions within those positions any power at all: if complexity and intricacy in the universe are a problem, then why aren't they equally a problem for god?

Oh, but god is "self existing," whatever that means. God just always was! And there you have the problem with theistic thinking: bare assertions and subtractions take the place of any meaningful justification of the claim. Many theistic arguments just don't bother to provide positive evidence for god at all, they seek instead to cut a god shaped problem into our understanding of the world that can be, so very coincidentally, filled by their particular god. Stripped of all the fancy philosophical language and intentional obfuscation, the majority of theistic arguments fall into the same formulation: "Here is a problem with the world, because there are rules in place that prevent it from resolving naturalistically. Here is an entity that is asserted to exist. It is the thing that solves the problem that is asserted to exist by breaking the rules that are asserted to apply to everything." It just invents a negative space that looks a bit like god if you squint, without ever bothering to establish that the thing inside that space is actually god, instead of just wishful thinking grafted onto an argument from ignorance.

For that which is self existing (non-contingent), I don't see that there is any logical necessity that this thing be either simple or complex, as it is not dependent on anything else for it's existence.   That which is the effect of something else, requires a cause, which is sufficient to explain that effect.  If that which is in question, is not the effect of something else, then I don't think we can make any demands as it must be this or that.  It would seem to me, that a first cause, must be sufficient to explain everything that came after and that you are working the other way around.  

Also I would agree with many current philosophers of religion, in saying that God is simple in nature not complex (composed of many parts).

Like this, for example: pontificating about what we can and cannot logically expect from a first cause, seemingly without care that a "self existing" first cause makes no logical sense on its own. God shaped hole, not god shaped god.