OK, so what's the difference between a credosphere and a meme? That was the question put by the same colleague after the last entry. A meme is an idea transmitted as an idea; it may remain the same, or mutate, or grow stronger, or weaker, or become extinct. An urban legend is a good example of a strong meme: The forgotten gods of our neolithic forbears a good example of an extinct meme. These ideas, these beliefs, necessarily need belief in order to thrive - they need to people to have faith in them as some kind of truth, a kind of 'good', in order to live. A credosphere is basically an area - physical or metaphysical - where a meme, or a set of memes, thrive.
The other difference is that if you can recognise a credosphere and you're cunning or powerful enough, you can influence that area, and subsequently all those individuals who fall within that particular area. One example would be in the theatre. Anyone who has been to a great performance of a play or a magician's show can attest to how they are held spellbound while the performance lasts, thanks to the skill of the actor(s) or magician. Another good example is of the call to patriotism in times of national distress - to believe in a core set of values, the centre of a creed. While it makes the core meme stronger, it also strengthens a counteridea. The Bush government's call to arms is ironically making its enemy more focused and powerful, both as an idea and as a physical form. Al-Quaeda started off as not much more than a loose set of (admittedly nutty) ideals; Now it is far more sinister in reach and capability, simply because it has been given form and shape, and a place in which to foment.
Credospheres, while inherently about belief, can actually inhabit a physical area - where, for example, you get several different national, linguistic or religious groups inhabiting the same city, you are most likely to end up with some kind of ghettoisation.