Begin with a turnip...

"It is very hard for a man to defend anything of which he is entirely convinced. It is comparatively easy when he is only partially convinced. He is partially convinced because he has found this or that proof of the thing, and he can expound it. But a man is not really convinced of a philosophic theory when he finds that something proves it. He is only really convinced when he finds that everything proves it. And the more converging reasons he finds pointing to this conviction, the more bewildered he is if asked suddenly to sum them up. Thus, if one asked an ordinary intelligent man, on the spur of the moment, 'Why do you prefer civilization to savagery?' he would look wildly round at object after object, and would only be able to answer vaguely, 'Why, there is that bookcase . . . and the coals in the coal-scuttle . . . and pianos . . . and policemen.' The whole case for civilization is that the case for it is complex. It has done so many things. But that very multiplicity of proof which ought to make reply overwhelming makes reply impossible.

"There is, therefore, about all complete conviction a kind of huge helplessness. The belief is so big that it takes a long time to get it into action. And this hesitation chiefly arises, oddly enough, from an indifference about where one should begin. All roads lead to Rome; which is one reason why many people never get there. In the case of this defence of the Christian conviction I confess that I would as soon begin the argument with one thing as another; I would begin it with a turnip or a taximeter cab."
–– Orthodoxy, chap. 6

Atheism can never have the same certainty or epistemic integrity as theism, since it asserts a negative. Atheism can literally never generate or obtain adequate proof of its core thesis. Even a direct encounter with God could be scoffed away as a delusion. How do you "prove," after all, that an infinite line is not really infinite? Moreover, from a pragmatic perspective, the crucial evidence can never enter the court in time. If it's true that we all just fade away into a godless universe, who would know? That fate can't count as evidence, since no one will be there to hear it. Atheists go to their graves literally dying with the faith that they are right. Upon death, they can only be proved wrong: they can never be proved right.

Theism, by contrast, can, and may, at some point be falsified. Even particular "brands" of theism can be falsified, say, at a final judgment in which, lo and behold, only one God presides--or, for that matter, a pantheon of gods presides! Theism is a positive claim that demonstrably makes sense of the whole shebang, whereas atheism is, intrinsically, a nominalistically grouped set of subjective protests by humans, explicitly made from ignorance, that "the world doesn't seem to make sense to me." To insist "I simply have no compelling knowledge of God," is an autobiographical statement about the atheist's cognitive and spiritual limitations. It is not anything like a proof about the reality of God as known by the faithful. As such, a theist is epistemically justified, even to be commended, for trusting in the existence of an all-good God, since this faith fully explains and grounds his other epistemic burdens. An atheist has no similar epistemic grounding for his claim that, based on the little he knows, there seems to be no God.

Interestingly enough, atheism is wrong only because it doesn't carry itself far enough. The world does "lack God," since God is infinitely transcendent from the world. As such, there is no evidence of God "in" the world. As Fulton J. Sheen puts it in The Life of All Living (New York: Image Books, 1979), "The white light of His nature shining through the prism of creation breaks up into faint expressions of His Infinite Perfections. As great as creation is, … there is nothing in it which reveals the inner life of God" (p. 46). Sadly, however, precisely this divine lacuna in the cosmos ought to propel the unbelieving mind to God as transcendent Maker of the world. Atheists want to find God "in" this world rather like a nanny wants to find a naughty boy "in" the closet or "in" the garden, but that is simply an illegitimate demand to make, as far as classical theism is concerned. To borrow a metaphor from Ric Machuga, God is not "in" the world the way dirt is "in" a carpet; He is in the world the same way meaning is in words: undetectably but undeniably. To cite Sheen again:

"Every object which the mind can discern is a letter of the living Word of God. Some men, always children mentally, play with the alphabet blocks as so many meaningless toys, never dreaming to spell the word, until it is too late––when the universe is taken away. Others, there are, who see meaning in the blocks, and it is these who learn to read the sentence that stands first in the primer of life: God made the world." (p. 44)

You can no more assert "There is no God in the world" than you can assert "There is no Meaning in language." In both cases, the term being denied is performatively immanent in the very action of denial. Using words to deny meaning presumes those words, at least, have meaning. Likewise, "citing" the world to deny its divine origin presupposes the world's ultimate rationality, its ultimate character of "making sense from an ultimate perspective." If there is a complete explanation of the world, there must be a mind which can grasp that complete explanation. It is precisely the ultimate intelligibility of the world, even when it is conscripted by atheism (à la Bertrand Russell in "A Free Man's Worship"), that theism refers to as "the Good Creation," and the ultimate perspective in which the world makes sense that theism refers to as "Divine Providence."