What I believe follows from this. Do you agree? In facing questions like the one you ask, it is important on the one hand to distinguish between "what has to exist" (sometimes called "necessity"), and what is "in need of an explanation" on the other hand. So, for example, while there is a formula for solving quadratic equations, which every high school student learns in algebra, there is no formula for the general quintic. It follows from this that if god were to exist god might know the solution to any quintic, but god would not be able to write down a general solution. Every quintic has a solution (in fact it has 5 of them and for the same reason that a quadratic has 2). This is a necessary feature of algebra; that is to say, it is necessarily true once one discovers algebra. Does it make sense for someone say, "Well, do you have any evidence for that?" Well, no, there is no "evidence" that a formula for solving the general quintic does not exist. Indeed, it doesn't really make sense in this case to ask for evidence: the assertion that there is no formula for solving the general quintic is still true because it is necessary. This is a product of how one works through the questions arising from thinking algebraically.
There are lots of situations where asking for evidence, asking for an explanation, seems to make good sense. Physics, chemistry, biology, botany and astronomy are good cases in point. It makes sense to ask, for example, "Why does the DNA in my mitochondria come only from my mother and not my father?" There is something very different about this question than the question about algebra, and it seems to be a type where asking for evidence seems warranted. Physicists, too, are bent on providing explanations of this latter sort, and they are careful when they meet questions of the former sort not to confuse the two. So, for example, good physicists will happily assert that everything we see around us is subject to needing an explanation: people, trees, water, the solar system, galaxies, sand, bacteria, states of mind; all stand in reference to this latter sort of questioning: "Why are things this way and not some other way?" This happens in the Astronomy section of Y!A all the time. "Why is the sky blue?" shows up with annoying regularity! So, why is the sky blue and not red? Why are all large solid bodies roughly spherical in shape? Why is the sun yellowish? Why is the solar system stable over long periods of time?
Care needs to be taken when lumping individual items into systems because not every attribute of a planet, say, becomes an attribute of a solar system. It is not always clear how explaining the parts of a system explains the whole system. For example, no good physicist would assert that a wall made of small bricks was, therefore, a small wall; but it would still be a brick wall. A pile of ten-dollar bills on a table isn't an "empty" pile when all of the ten-dollar bills are spent. None of us would assert --except as a joke-- that the world is littered with empty piles of ten-dollar bills. So, it makes sense to ask "How did this pile of ten-dollar bills get here" without the answer being "Well, the pile was always here, it just has ten-dollar bills now, whereas before it was just an empty pile." The pile itself is susceptible to the same sort of questioning that the sky is, that the solar system is, that my DNA is. In a larger context, it makes sense to ask how did the universe as a whole get here without the answer being there is no universe as a whole.
At each step in this process of asking questions we always ask for a set of reasons (sometimes those reasons give evidence and sometime they do not) which give us some explanation for what we see. When do we ever stop asking for an explanation or for evidence? When we cite reasons which are perforce necessary. For example, there is no equation from which one can derive the positions of the planets of our solar system. This is called, in the parlance of mathematicians, the "n-body" problem. If the solar system were composed of exactly two bodies which were themselves perfectly rigid spheres, and if they are reasonably small and at a great distance from each other, then there is such an equation which was derived by Newton. But when the number of bodies is greater than 2 then no such formula exists. There are *numeric* solutions which can be quite good over long spans of time; but no general solution. No physicist searches for one; what's the point? Likewise, absolute zero is what it is. Occasionally on Y!A physics, one sees the question "can something get colder than absolute zero?" Asking that question makes clear that the person asking does not understand what "absolute zero" means, no why it follows from the way one thinks in the process of discovering physics.
So, when one faces all that physicists, biologists, psychologists, chemists, geologists and astronomers have discovered it does indeed make sense to ask, "Is there a reason for all that exists, for the universe as a whole?" One can, of course, choose not to ask this question, one can minimized the question, but those are personal issues of integrity; yet as the discussion shows this question --how did the universe as a whole come to be-- still makes sense to ask.
The answer to that question is what Muslims, Jews, Christians, Taoists, Wiccans, and the like refer to when they use the term "god." As a consequence, there is no "evidence" for god, nor does god need further explanation. Quadratic equations have a general formula for their solution, the n-body problem is not solvable, god is the answer to a particular question and there is no "going beyond" these. There is no good way to answer the question, "Well, can you give me some evidence that every quintic has a solution without an explicit formula?" It follows from a whole way of thinking about algebra that it is so. The same is true for god. As I pointed out, god is the answer to, god follows from, a whole system of questioning.
HTH
Charles