I have a vaguely Buddhist notion in mind with this now that I think more about it.
As seen in the real world 1st World nations these days, once you have enough material comfort, spiritual comfort in the "next life" doesn't seem so necessary. People in 1st World nations typically don't have the struggle for existence still seen in many 3rd World nations and so the idea of believing in something that will reward you for all your suffering in this life, isn't particularly relevant.
Hence we see a lot of people that are agnostic (in that they still have a belief but don't particularly follow anything) or atheist (as in, choosing to live without any religious influence over their daily living). Once you've reached the stage where you're no longer struggling against nature and your fellow man just to stay alive for a few more years, the trappings of religion seem a bit unnecessary.
So once you're at that stage, spirituality would be achieved by improving yourself rather than entreating some unknowable entity to save your worthless hide, divesting yourself of material desires and emotional complications, in other words, obtaining ultimate enlightenment (or in Buddhist thought, nirvana).
But once your society has reached a technical level that allows you to manipulate the world around you as if you were a god, then perhaps enlightenment requires something more than just divesting yourself of your love of a comfortable life with its fully stocked pantry, large screen telly, swimming pool, two cars and 2.5 kids.
So perhaps you need to expand your intellect to the point where you can comprehend multiple dimensions? Expanding it far beyond your everyday interactions with the physical world and even technology. But how do you reference and then gain understanding of the world beyond what you know?
Chaos Theory, Geometry and Fractal Mathematics...
Phulish mentioned scientist/philosophers, in this instance, your whole society would be scientist/philosophers... well, those who got the right education would. The less intellectually proficient would probably form the drudge work manpower pool (e.g. military personnel, maintenance personnel. Which could lead to spiritual schisms between the enlightened and the unenlightened
In regards to DC, certain alien races might even have a symbiotic relationship with a less intellectually advanced race, the less proficient race performing all the crap jobs so that the intellectuals can pursue their enlightenment... until they all crash headlong into the nearest Dark Lord who says "Bow down and worship me or I'll eat your soul".
Well that's my train of thought anyway.
Strangely enough, as I was thinking about all of this, I had a recollection of the Maggie O'Neill character, Dr Tucker from the mini-series
Invasion Earth being stuck in an alien dimension - must try and find that show on DVD and watch it again.