I was just reading a book on this subject recently, so let me quote a bit that deals with such questions:
“There is a real danger of arguing in a circle and finishing up where we started. If, for example, I begin with the assumption (hypothesis) that ‘a God exists who created all things’, I cannot subsequently use the existence of the universe as an argument for the existence of God. In other words, reasoning that goes as follows is invalid:
1. A God exists who created the universe.
2. The universe exists.
3. Therefore it must have had a creator (a God who created the universe).
In a valid syllogism the statements (1) and (2) would lead to a conclusion (3) that is not contained in either (1) and (2), but in this example we simply end up by deducing what we assumed in the first place. Interestingly, if we abandon the hypothetic method and remove proposition (1) we also remove the fallacy and arrive at what is, in essence, the traditional ‘cosmological argument’ for the existence of God (which reasons from the existence of the cosmos to the need for a ‘first cause’). However, as we shall see, there are distinct advantages in persevering with the hypothetic approach in spite of the potential pitfalls.
A further example of circular argument is the idea promoted by some atheists that ‘science disproves the existence of God’. The assertion is based on the claim that science presents no evidence for the existence of supernatural forces or phenomena. It sounds plausible until you look a little more closely. The argument can be expressed as a syllogism as follows:
1. Science is the study of the physical universe.
2. Science produces no evidence for the existence of non-physical entities.
3. Therefore non-physical entities such as God do not exist.
Again the fallacy is clear. In point (1) ‘science’ is defined as the study of the physical or material world. This statement thereby excludes by definition any consideration by science of non-physical causes or events. The proposition then argues from the silence of science concerning non-material realities that such realities do not exist. By the same logic, if you define birds as ‘feathered creatures that fly’, there’s no such thing as an ostrich. It’s fairly obvious in this example whose head is in the sand. The correct conclusion, of course, is not that ostriches are mythical birds but that (on your restrictive definition of ‘bird’) they are not birds. In the same way, to define science as the study of the material universe simply prohibits science from making statements about a non-material entity like God. If the remit of science is deliberately restricted to the physical realm, the fact that science (so defined) tells us nothing about God has no bearing whatever on his existence or non-existence, as most scientists recognize.”
I hope that lengthy quote helps you see why the idea of anything being “required” for the universe to exist is a false premise. Now, Scientists cannot object to theists advancing ‘the hypothesis of God’ in which we assume that God exists, then see where it leads – for theists would just be following the example of the string theorists and science in general. They propose a hypothesis and explore where it leads to. But if you set a limitation on an idea at the outset – that God is NOT required for the universe to exist – you are choosing to ignore the possibility that the universe might exist because of God. In other words, you are prejudiced.
“Who Made God?” by Edgar Andrews pp 56-59 (EP Books, 2009)