Matt Dillahunty has articulated what I consider to be the most lucid and reasoned explanation for why he should be an agnostic atheist as opposed to the "hard" variety. He states that while there is no good evidence or argument that would compel him to accept the outrageous and absurd claims of religions, he also admits that he is unable to meet the burden of proof required of someone who claims to know with certainty that there are no gods or goddesses.
I happen to agree, from what I know of him, that in all likelihood Matt Dillahunty is not able to meet that burden of proof. Most people on the planet would not be capable of meeting that burden of proof. However I would not go so far as to claim that the burden of proof is impossible to meet, or that no one on the planet can now or ever do so.
So, hypothetically, what would it take to be able to definitively state as a matter of demonstrated fact that gods and goddesses are not real? That there is definitively and provably no god?
Step one is to recognize that "god" is a word linked to a broad and poorly-defined category of nebulous, shape-shifting ideas. Attempting to connect such a word with any actual evidence is like trying to state anything definitive about Zlypph. Who or what is Zlypph? Not telling. You have to figure it out and prove that it is or isn't real. Well, this is a pointless task, unless we can attach some actual meaning to this worn-out placeholder.
We therefore go right ahead and do exactly that - attach some actual meaning to the word that is more than the vague bewildered gooey feeling ignorant people get in their brains when they are sad or can't comprehend something. We must pin languages' most shape-shifting word to a specific meaning, such as "a universally powerful intelligent agent." Even without all the adornments that various religions hang onto this definition or the numerous properties, characteristics, agendas, likes or dislikes that vary from one god to another, this, surprisingly, is enough for us to proceed.
Now, let's imagine that an individual has access to some unspecified but sufficiently large amount of reliable knowledge. And by "reliable" I mean of course scientific knowledge. Science as we know is the most reliable process for knowing things. Compared to Science, every other way of knowing is no better than random guessing, and often considerably worse. This is a direct result of the way Science always seeks disconfirmation rather than confirmation. It is almost impossible for a false hypothesis to withstand skilled and determined efforts to disconfirm it using repeatable empirical evidence and unassailably rigorous analysis consisting of both logical and quantitative reasoning. Only something that is reasonably true, that is, having a reasonable concordance with the real universe, can stand up to that kind of treatment. And so, scientific knowledge is the only reliable knowledge.
Using unlimited access to this scientific knowledge along with the resulting comprehension of the natural laws, principles, processes, matter, objects, forces, fields, effects, or phenomena of the real universe, including the biosphere and its development on this planet, such a broadly informed person could be in a position to ask himself, "Is there some all-powerful (or nearly so) Agency at work in the universe?"
In order to answer in the affirmative, our polymath scientist would have to identify two enabling circumstances that are necessary but insufficient conditions. In simple terms, these two things have to be found in order for gods to be real; but even then only producing an actual specimen would prove it beyond doubt.
Those circumstances are as follows:
1. We must see evidence that such an agency is or has been active. We must observe objects, circumstances, processes or incidents that positively have no natural explanation or ordinary human or animal agency as their cause. So far, all of the vast quantity of evidence that we have can be readily accounted for using natural processes or animal/human agency. There is no evidence that the universe is or has been influenced in any way that only a powerful universal Agency could produce.
2. We must be able to identify specific processes or mechanisms by which this influence occurs or could occur. That is, what is the entry point or point(s) of contact between this Agency and the physical universe? We have thoroughly and meticulously scoured all of the possible physical interactions over a wide range of energy levels from the smallest weakest particles to the most powerful forces and objects in the cosmos. What we know is that there are three and only three forces operating on matter and energy: the strong nuclear force, the electromagnetic/weak nuclear force, and the gravitational pseudo-force.* We know and it has been demonstrated that there are and can be no other forces operating in these regimes. We know how those forces work and all the ways that matter and energy interact through those forces. We know that, within the limits that can possibly affect objects ranging from electrons up to massive stars, there is no other way for the physical universe consisting of matter and energy to be influenced other than through these forces acting on these particles.
The absence of evidence where that evidence MUST exist is definitive evidence of absence. Therefore there is positively no supernatural, no magic, no ghosts "outside" the universe sticking their hands in and tweaking or nudging it, or any such thing. The mechanisms that would enable such influence to occur would have been evident exactly in the places we have been searching.
We also have zero evidence that such influence has been taking place, and certainly with nothing like the regularity that theists claim it is occurring. Again, the absence of this evidence is the evidence.
If you have been paying close attention, you may now be objecting that we have actually been evaluating the claim that gods exist, rather than the claim that they do not. We have actually assumed the burden of proof of the deists/theists. But a careful examination of the scientific evidence allows a sufficiently informed individual to conclude that the evidences or lack thereof for one claim are the same as for the opposite claim. In particular, that the singular absence of evidence for the claim made by deists is precisely all the positive evidence needed to meet the burden of proof required of the gnostic anti-deist.
Now, if theists propose an even more narrowly specified god having particular qualities, properties, likes and dislikes, taking specified actions at specified times, then it becomes even easier to locate the (lack of) evidence required to disqualify and dismiss such claims, again positively. The positive presence of a big empty hole where the theists' evidence was supposed to be is itself the evidence.
Not everyone has access to a sufficiently deep and broad range of scientific evidence and knowledge sufficient to enable one to positively conclude that the theists' evidence is actually missing. It's too easy for most people to not know for certain that the evidence is not in some other field with which they are unfamiliar. Theists take advantage of this information segmentation or compartmentalization and deftly shift from one claim to another depending on what areas his debate opponent is least familiar with. But it is not impossible for some generalists in the basic sciences with informed interests in a wide range of other fields in pure and applied sciences to actually be capable of synthesizing all the information necessary to positively, definitively conclude that there are no gods.
My perception is that there are typically more hard atheists among scientists than among other walks of life. But I do not fault Matt Dillehunty for remaining agnostic. On the contrary, I applaud his honesty for refusing to claim that he can meet the hard atheist burden of proof. But he should not also fallaciously conclude that since he cannot, no one can.
Nor do I call for Matt to change his position. He should not, and I support him in his position. For one thing, his acceptance of scientific evidence without actually understanding or evaluating that evidence would be nothing more than an appeal to authority, which is just one more of the unreliable ways of knowing things that rational people deplore. But more importantly, Matt can do what few hard atheists can: connect and engage with people. Matt can build bridges, whereas scientists like me are only good at being divisive and intolerant. He is more gifted in that area than I can ever be, precisely because of his refusal to adopt the hard atheist position. No, Matt, we need you where you are. You're good.
*But what about dark matter/dark energy? We don't know what those are yet, so there could still be gods and magic, right? Wrong. These effects are not observed except on objects the size of a galaxy or bigger. So we ordinary people, stars, and planets are unaffected by these forces. But Your Mama should be more careful.