ONE OF THE BEST ARGUMENTS  for the wisdom approach was penned by Carl Rogers, the famous psychologist, and can be found in The Carl Rogers Reader (a book that should be required reading for anyone who dares to comment on "human nature"). 

Rogers compares humans to other animal species, and observes that there is no such thing as an evil species. Taking the lion as an example, he says:

He kills an antelope when he is hungry, but he does not go on a wild rampage of killing. He eats his fill after the killing, but there are no obese lions on the veldt. He is helpless and dependent in his puppyhood, but he does not cling to the dependent relationship...

...Lions satisfy their sexual needs, but this does not mean they go on wild and lustful orgies. His various tendencies and urges come to a continual changing balance in himself, and in that sense he is very satisfactorily self-controlled and self-regulated. He is in basic ways a constructive, a trustworthy member of the species Felis leo.

And, based on his years of experience, counseling every sort of person, Rogers concludes:

In my experience, to discover that an individual is truly and deeply a unique member of the human species is not a discovery to excite horror. Rather I am inclined to believe that fully to be a human being is to enter into the complex process of being one of the most widely sensitive, responsive, creative, and adaptive creatures on this planet.

So, for me, spirituality consists of valuing the human spirit, of rejecting the legalistic notion, in practice, that the human spirit is "bad" or "fallen", of working to understand my own nature, and that of my fellow humans, better.

It also consists of seeking ways of acting and being that help to bring out the goodness we all have in our inmost selves.

Spirituality can be practiced within a religious context, but it is not necessarily a religious activity. It does involve faith—small-f faith, in the sense of trust, based in experience, of the human spirit (as opposed to Faith, in the sense of blind belief of religious dogma). 

It's a matter of trying to be honest with yourself—not kidding yourself about your motives or behavior or beliefs—and it's a matter of listening: both to yourself and to others.

It's a matter of being aware of what's happening in the moment, of giving respect to other people and to yourself, of enabling the goodness in human nature insofar as you can.

In this sense, then, a person is spiritual insofar as he or she assumes that the human spirit is a good thing on the whole, and attempts to understand and cooperate with it, rather than working against it.

This is why I believe that the legal model represents a false spirituality. It pretends to be on the side of the human spirit while it really is against the human spirit. This is particularly ironic in the Christian tradition I come out of, because the Bible clearly says that the human spirit is an extension of God's own spirit.

Whether one is an atheist or a Christian, the idea of a spirituality which is centered on repressing the human spirit involves an inherent contradiction.

So, to those who see a contradiction between the words "spiritual" and "atheist", I offer the above two definitions:

1. One can be a "spiritual atheist" in the sense that he or she doesn't believe there is a supreme being, but does believe there is a spiritual side to reality.
2. And one can be a "spiritual atheist" in the sense that he or she not only believes there is a human spirit, but regards it as fundamentally good, in practice.

One doesn't have to believe in God to believe there is such a thing as the human spirit—that we really do hurt, and have joy, and love, and yearn.

One doesn't have to be religious in order to trust and value the human spirit.

I don't believe, however, that this view of spirituality, rooted as it is in both common sense and the wisdom approach, is only possible for an atheist. There's nothing about the belief that the human spirit is both real and trustworthy which is antithetical to religion, or even theism, in general.

For this reason, I think the phrase "spiritual atheism" should be reserved for situations where the actual topic has to do with whether an atheist can, or should, be spiritual (in either or both senses).

For the most part, I prefer the phrase "natural spirituality", which is much more welcoming to both the religious and non-religious, theist and atheist, alike.