The idea that an atheist can simultaneously be spiritual is as counter-intuitive as an idea can get. Someone who is capable of believing in metaphysical things while being unable to see evidence in favour of their being anything of the sort is someone who must be lying somewhere. It is oxymoronic in every possible way.
The spiritual argument for why is doesn’t is extraordinarily simpler, and perhaps effective, than the Atheistic side. This book is the word of god and the book says god is omnipotent and benevolent, therefore everything in the book is true. At the same time there are those who simply relinquish any pretext on what god could be or want. They simply say I feel it and so it is. Evidence to the contrary is irrelevant because it’s not about evidence.
The Atheist argument pretends to be more logical, but really isn’t. It dismisses what people have said and replaces it with what can be seen. It builds the book and cites its sources, allowing others to critique and challenge it. And so far hasn’t been able to find evidence of a god anywhere. For the atheist with an interest in explaining how something political can be an absolute truth, and how something can be the right thing, it can lead to an endless maze of roadblocks.
The ability to justify anything as being the correct answer runs into the inconvenient truth that the world itself provides no indication as to what it could be. All of our commonly held pleasantries are often obviously relative and our deeply held rights are exposed through logic to be the same. One thing we can be entirely certain of is that entire cultures have engrained in their people the sensation that this is right and the sensation that their justification for it is right.
In fact, every major religion and philosophy shares this conviction as a common feature and so while the atheist may disagree with the justification for ideals, they must submit to the fact that the sensation is real. The tens of thousands of religions that have ever existed all share with each other something that is other than this world, and all religions can testify that this being has been experienced. In light of this the atheist must once again concede that the sensation of being in the presence of something greater isn’t a lie.
It may appear to some that from these certainties it becomes impossible to justify atheism, this is not true. The sensation of being part of something greater is so prevalent in every religion we study that it would be foolish to assume someone who doesn’t believe in something other, can’t believe in something greater. Anyone familiar with the Overview Effect has if not a direct understanding then a second hand understanding that it doesn’t take a spirit to experience what has so often been understood as a spirit. Anyone who has spent a few contemplative moments listening to Carl Sagan explain the Pale Blue Dot, or fully understood the old proverb that we are star dust, may have been lucky enough to experience an incredible sensation. The feeling that we are part of this universe and integrated into it often leaves the impression of a great magnitude upon the psyche. Put simply those lucky enough to have such a spiritual experience know, with as great a certainty as a Christian, Muslim, or Hindu experiences their god or gods, that we are a fold in the universal fabric that has developed the unique ability to look back upon itself.
In this way the atheist is spiritual because they experience the exact phenomenon that those with a god or gods experience. The sensation is undeniably real and it is not restricted to only those with something outside of the physical world.