[W]hereas I and other scientists are humble enough to say we don’t know, what of theologians like McGrath? He knows. He’s signed up to the Nicene Creed. The universe was created by a very particular supernatural intelligence who is actually three in one. Not four, not two, but three. Christian doctrine is remarkably specific: not only with cut-and-dried answers to the deep problems of the universe and life, but about the divinity of Jesus, about sin and redemption, heaven and hell, prayer and absolute morality.
When I design circuits, unless the circuit is something as simple as feeding the right amount of juice to an LED, I don't have the doubtless confidence of telling myself or the world that I know it's going to work perfectly, flawlessly. As is typical and standard practice, I go over the design a number of times, recheck my calculations, and then breadboard the whole thing, crossing my fingers that I don't blow a fuse or fry an IC (again). A crucial part of the design cycle is testing. However confident I may be that a design is ok, I can never be absolutely certain until I build the circuit, power it up, put it through its paces, and see whether it does all the things it's suppose to do. (and even then I can't be certain that I've not pushed any component to its operating limit, including thermal limit, thus leading to possible early failure).
A circuit design issues from the brain. It may or may not work. And when one's a novice the odds are in favor of unwittingly zapping something or turning out a lemon. The only real way to find out whether it actually works (and how robust it really is) is to build it and power it up. Testing is all important in order to validate our belief that the design works. (Yes, I'm aware of simulation software that can obviate some actual hardware testing. I actually use Microchip's simulation software whenever the design incorporates one of their PIC microcontrollers)
Theologians, religionists who insist that this and that theological claim is true, on the other hand, are perhaps some of the most hybristic people in the world. How can they possibly claim to know and insist a certain claim about the supernatural is true when they haven't checked whether what their brains have churned out is in fact in consonance with reality? When they haven't tested the validity these ideas? And how can they simply trust--have faith--in these claims despite or because of the fact that these claims can't ever be tested and checked for validity/veracity? There's something very wrong in this line of thinking and behavior.
It's actually much worse. Those who design circuits have various premises. For example, I take for granted that (nondefective) diodes conduct only when there's a positive potential difference between their anode and cathode, but not the other way around. I don't go about questioning this assumption. Why? Because there already exists much evidence that this is so. Furthermore, if someone, including myself, were to question this claim, it can always be tested. Another example. One of the most important equations in electronics is Ohm's Law. V = IR, where V = voltage (in volts), I = current (in amperes), R = resistance (in ohms). Again I take it for granted that this law holds. And again those who are skeptical of it can always build a circuit using precision components and test this equation's validity to their satisfaction. While it may seem that we take certain things on authority, the fact is that not only are the presumptions backed up with evidence, but also that they are testable and can be proved (or disproved) if one wishes to do so.
What about theological premises? None of them are known to be true. And they can't be known to be true--they are untestable. Now if the facticity and veracity of the premises are not known to be true, then no argument or conclusion founded upon them can be known to be true. When it comes to theology--whether Hindu, Zoroastrian, Muslim, Christian, or what have you--there is no claim therein that is known to be true. Every one of them is at best a hypothesis.
So what in fact do theologians know when it comes to the supernatural? Isn't it that they're merely spouting fantastical, unverifiable claims and performing mental gymnastics?
If we claim to know then we must be able to elucidate a valid way of actually knowing it, and show that what is being declared is in fact true. To say that we know through revelation or through authority or tradition--these are illicit and vacuous ways. Just to tackle revelation: Because we know that humans are unreliable (would you really fall on your knees and lend your ears and brain every time someone claims s/he's received a communique from his/her deity?) all so-called revelations need to be tested and checked. But how do we test whether a claimed revelation is not just a misfiring of neurons, or a result of some illness, or a mere delusion, or some other thing? Is there a way of doing so? And of course there are more fundamental questions: How do religionists know that revelations really exist? Is there at least one indubitable instance that they can cite? If so, how do they know it really was a revelation? And is revelation not the same as intuition? How do we definitively and testably differentiate one from the other?
Thus, I cannot but agree with Dawkins when he asks whether theology is a subject at all. What could theologians be experts in? Well certainly not in phenomena that are or can be known to be real, in claims that you can go check and confirm/disconfirm. If you ask me, devoting half a century of one's life to theology is a pitiable waste. It's not much better than spending the same amount of years in becoming an authority on the Lord of the Rings. The thing about theists that sets them apart from Shakespeare, Rowling and Tolkien experts is that the latter know their expertise is in works of fiction. Theists have the delusion that their claims are in consonance with reality, that they know of an otherworldly reality.