The Power of Belief

It's said so many times that a basher doesn't hear it anymore. Risking that, it should be stated again: Belief is power on the Planes. But what does that mean? It doesn't mean that if a berk really wants a ham sandwich, he only has to believe he's got one and BAM! it's there. Bar that. Any leatherhead knows that life's not that sodding easy.
It does mean that belief can affect reality. It's not a free wish, but it's an undeniable fact that the laws of the multiverse respect beliefs and those who sincerely hold them. Things just work better for a blood with strong convictions. As a cutter figured out what he believes in and acts upon those beliefs, he becomes attuned to the planes. Tiny secrets are revealed to him. It all starts to make sense.
Here's the real dark of it though, and this is something no faction member will understand or accept: The act of believing itself is the key, not any particular belief. In the end it doesn't seem to matter what a body believes so much as how strongly he holds that belief.
In some places, the multiverse is so receptive to belief that it responds to one's outlook and conscious view of things. On some of the Inner Planes, "down" is relative to what direction a body believes "down" should be. Other planes have similar quirks. Limbo is an obvious example of how will and outlook can directly create something stable from absolute chaos. And look at the powers - even they ultimately rely on their worshippers' belief in them for their own might. Take that away, and a power'll fond himself floating an the Astral with the rest of the dead gods.
So, what happens when a group of berks walk into Sigil and believe the Lady of Pain away? Nothing at all - except maybe they'll get flayed. The point is...we'll they've missed the point entirely.

Belief on the Planes

Belief's a strong, straightforward sort of thing. Its effects on the nature of things are subtle and slow. Most bashers never even notice them. Belief and action are tied together in ways too numerous to count. Action gets results and changes the multiverse - and not just in a direct manner either. If enough people in a gate-town act (and believe) in a manner representative of the plane the gate-town leads to, the burg ends up shifting to that plane from its position in the Outlands. Entire layers of planes have moved because of similar occurrences. The actions and beliefs of thinking beings tie directly into the fundamental aspects of the multiverse.
So what does that mean to the individual? A body still can't just believe that things will happen a certain way and count on it. What advantages does a person with strong convictions have over a basher with none?
As mentioned above, things seem to work a little better for a cutter with strongly held beliefs. She reaches a state of harmony with the multiverse, giving her what some call luck, some call karma, and others simply call providence. When climbing a wall, she knows just the right hand holds; when fighting, she knows the perfect moves; and when threatened, she knows exactly when to duck.
Additionally, such a planewalker begins to develop a trustworthy intuition. In times of need, her "gut instinct", as it were, is as reliable as hard facts are to others. If she's lost, she can figure the best way to go, and there's danger, she's forewarned by clues others might miss and stands prepared to deal with it.

Who Believes?

Some leatherheads think that only clerics and paladins need strong convictions. Well, they're half right. While anyone can believe in something, priests and paladins already maintain a system of belief based around faith and dogma. Thus, any system of belief is automatically skewed toward those classes, since they're accustomed to cleaving to their beliefs. That's just the way of the planes.
A good many of these folks' beliefs are determined for them by the teachings of their religion. Such individuals must follow this religious dogma to maintain their standing, not to mention to keep their god-given abilities. Priests and paladins can easily hold beliefs different from their religious creeds as long as the beliefs aren't contrary to those set forth by the religion.
But religious individuals aren't the only ones who have their beliefs decided for them. Those belonging to a faction have a certain set of their beliefs determined for them as well/ Faction doctrine is often as strict, or stricter, than the tenets of religion. And, just like priests' and paladins' spell-casting abilities, faction abilities stem from belief. Berks don't have to believe in their factions teachings to be members and gain the simple benefits of mere membership, but they must believe in those teachings to access the special abilities granted to faction followers.
Both religious and faction-oriented folk with an above normal record of adhering to their beliefs gain recognition from their respective organisations. While cutters with the strongest beliefs don't always become high-ups in such groups - in fact they usually don't, since their strong convictions may hinder their abilities as leaders -they often obtain positions of great respect.