A popular pulpit-sport among Christian preachers is to dream up utterly preposterous notions out of thin air and then claim that these ideas are what atheists believe. One such idea is that the entire universe must have just randomly popped into existence as the result of a great cosmic accident. I have never heard that idea expressed by anyone in the atheist community, but it might be worth examining anyway.
Randomness is a well-studied mathematical subject. Mathematicians and theoretical physicists have used the principle of randomness to aid in describing many of the phenomena of the universe. Now, does this mean that randomness alone could have caused the entire universe to exist? Of course not, and no rational person could believe it. However, if randomness is part of Absolute Truth, it is capable of being an uncaused cause of a few of the features of the universe, and these features have been well-defined.
Chaos sounds a lot like randomness to me, but competent mathematicians have assured me that it's an entirely different principle. It, too, has been well-studied, and, if it's part of Absolute Truth, it's also a possible uncaused cause of certain well-defined features of the universe.
Is logic valid! Nobody has yet succeeded in publishing a rigorous logical proof that logic is valid, but an enormous body of empirical experience exists to overwhelmingly support the contention that logic is valid. If logic is valid, then all axioms derivable by using the principles of logic as the only premises are absolutely true in all possible realms of reality, and can be uncaused causes.
For instance, consider the axiom, "If A=B and B=C then A=C." If this axiom is true, then it is the uncaused cause of the measurability of all dimensionally definable things. For instance, everyone realizes that you don't need to take your entire washtub to the hardware store to buy the right size drain plug, you only need to take your little pocket ruler, after having measured for the size you need. A is the size of the drain hole, B is the mark on your ruler, and C is the size of the plug. (If that axiom is not a part of Absolute Truth then maybe there's another universe in which rulers do not work, but let's not go there just yet.)
Many other axioms are also derivable from logic itself, and these, too, are uncaused causes and their effects are known and have been well-studied.
Many apparently non-axiomatic mathematical principles are behind many of the laws of physics. We don't know whether these principles are part of Absolute Truth and thus are uncaused, or whether they are only true in our universe and thus have unknown causes. But at least we know that they have effects, and we know what many of the effects are.
Now, are randomness, chaos, logic, axioms, and non-axiomatic principles enough to account for the existence of the universe? Well, probably not, but at least we do know that these things have been empirically observed in ordinary reality and their effects are definable without resorting to supernatural explanations.
Can our esteemed clergy make equivalent claims about this God they so dearly want us to believe in? I don't think so. Every theologian's description of God is different, and none of them are supportable by observations. Except for a vaporous assertion about something called "Omnipotence" (a poorly defined weasel-word at best), no theologian I know of has ever provided a description of God that includes attributes that imply creative powers.
The explanation "God created the universe" sounds suspiciously like the Great Cosmic Accident that our preachers take such great delight in accusing atheists of believing in.
Now, don't get me wrong! I'm perfectly aware of the possibility that Ultimate Reality may consist of a non-materially hosted conscious intelligence of some sort. But I see no justification for believing any such thing until it's been verifiably observed by enough people to at least agree on a few of its attributes.