This always amuses me. You say that the natural world itself must have a cause, and you think that this is a conclusion based on the observation that “all things within the natural world are subject to the principle of cause and effect”. For this to work, the natural world itself must be within the natural world; ie, it must be subject to the same laws as the things within it. So in this sense, it is subject to itself, and if you are comfortable with this level of self-reference, then I don’t see any reason why you shouldn’t be comfortable with the idea that it ‘caused’ itself.
But in any case, let’s go with it and say that ok, the natural world itself does need a cause. You say that the cause must be God. But if God caused the natural world, this implies that He himself is subsumed under the explanatory power of cause and effect, which would mean that, as well as being part of the natural world, he needs to have a cause himself. I regress to tell you that this presents the problem of when the buck stops with causality – it could just as easily stop with “the natural world” as “God” or “God’s cause” or “God’s cause’s cause”, etc. Your glib answer is that God is not caused. But if God is not caused, then he is not subsumed under the explanatory power of the principle of cause and effect, in which case the statement “God caused the natural world” is not, in fact, a conclusion based on an observation of the principle of cause and effect, but merely a faith statement, and a rather ad hoc one at that.
Seeya