Note: Although this is on a game website, I cover various different spectrums of entertainment. There is a slight focus on films because it is a more prominent means of telling a story than games (despite a recent advancement in games that tell stories) and I mostly came up with the thesis whilst thinking about film in general.

It's become a fairly common habit of mine to ponder the motives of characters in films beyond what we as an audience are shown. Sometimes subtle hints pave the way to deep musing and sometimes lack of development leads my inquisitive mind to fill in the gaps. Sometimes I just get so engaged that I can't help but speculate furthur. And along the way I've come to an understanding that there is one law based around one letter of the alphabet that tends to sum up all films in general and the incentive that drives them. In fact, you could probably go so far as to broaden the idea into any form of entertainment or 'art', providing you don't get too specific. If I were to narrow the gap down as much as possible it would be to say that this law tends to focus on stories and any medium which tries to tell a tale. And the letter, in case you're wondering, is 'C'.

Conflict
Let's face it, how many great stories have you read, watched, heard or generally experienced which didn't come down to some form of conflict? Even jokes tend to start with a point of conflict. "An Irishman, Scotsman and Englishman walk into a bar." Well, logically the first thing you'd imagine them doing is getting a drink and then they have to choose which one they'll each have and frankly, we haven't even gotten to the bulk of the joke yet. This is just the set up. Conflict is what drives all stories and it's what keeps them interesting. You don't even have to consider any great stories to find conflict, either, all the boring and mediocre ones tend to focus upon it equally. For a time, it eluded me as to why this seems to be such a necessary crutch for all our entertainment to fall upon but eventually it came to me...if you spent 2 hours watching someone achieve everything they've ever desired, just find it on their lap in a whim, how depressed would you feel about your life? No conflict means no effort, so it's hardly a heartwarming underdog story. Without conflict, we're essentially reading a tale about how Spot the Dog went to the park one day and had a great time, and unless you're aged between 3 and 5, that's never going to be particularly entertaining. Plus, even Spot the Dog usually got lost or something and had to wait for his mum to find him...
It's only in the most shallow and heart-wrenchingly putrid of stereotypical teenage pop songs that conflict seems to not play a part when it comes to entertainment and I'm not sure there are many educated people who would go so far as to consider said songs as particularly artful.
So, if Conflict drives entertainment, then what drives conflict? Every form of entertainment that follows the rule of conflict follows another rule of C and it's actually kind of depressing when you stop to think about it long enough. Our second C is of course...

Coincidence
This is where things start to get tricky...
At the beginning of the video game Bioshock, the main characters plane happens to crash into the ocean, just above where an advance city is hidden under the ocean...
15 minutes into Fight Club the Narrators apartment just happens to blow up mere hours after he met an intriguing stranger whose contact-card he accepted.
In the Harry Potter books, Harry just so happens to be the only wizard alive who is seemingly immune to his arch-enemy's magical abilities.
And every rock song ever just happens to be completely ironic when compared to one's own life and seems to channel the same level of angst many people suppress.
If you haven't figured out by now that none of these events are in fact coincidences, maybe it's time to wake up. Coincidence is something that developers, authors and writers call upon in every story in order to instigate events. Give them a little kickstart and whatnot. "Character A just happened to be in Place B when Situation X occured."
However, as in the above cases, coincidence can be manipulated, even revealed to be far from coincidence.
Let's take Bioshock for example and I think now is as good a time as any to post a big fat warning.

SPOILERS ARE BELOW, SCROLL DOWN IF YOU DO NOT WANT TO READ, BUT DO WANT TO MISS MY POINT
It turns out, as the plot progresses in Bioshock, that the plane crashing was not coincidence, but was in fact all manipulated by the supposed villain of the game Andrew Ryan. The player is not even a standard human but a clone whose very existence was in fact calculated to take part in a grand scheme of events that were taking place long before his birth.
SPOILERS ARE NOW OVER, RESUME READING BUT DON'T BLAME ME IF YOU DON'T UNDERSTAND THE REST

So, surely, that's void of coincidence right? It was all carefully manipulated, surely. Wrong.
It doesn't matter how in depth the writer manipulates the circumstances for the player, main character or events in question, the more you follow the timeline back, you're always going to find coincidence.
Consider your own existence: Your parents met, hitched up, and you were the result. However, even if they planned to have you as a child, manipulating when would be the right time to have you, it was still a coincidence that they met. Maybe your Dad's friend manipulated that by introducing your parents, but it's still a coincidence that your Dad met his friend. Follow the time-line back far enough and you find coincidence. But seeing as we're comparing to the real world now, there are some issues that really need to be taken into account.
Well, not so much some issues, as one specific issue: God, or whatever you want to call him/her/it, be it Shiva, Destiny, Karma, whatever. If you believe in this higher power that has ultimate control, coincidence is nothing more than a fallacy because this Superpower has the ultimate ability to manipulate everything and by putting our existence into place, has already done that.
When God created you, me and everything, it created us with the knowledge of how we would come to be, how we would live our lives and how it would end. It knew already, because it put it into motion. God isn't a scientist, experimenting with gadgets, God is a being that has infinate control and no random switch. And by comparison, the Equivalent of God when it comes to stories is whoever wrote or came up with the story. They created it with the knowledge of how it would play out.
The trickiness I mentioned is breaking the fourth wall by analysis, rather than characters talking through the television screen to you.
Let me try and dumb things down a bit.
In the movie, Slime Monsters 2, the character Jack engages in conflict by being eaten by one of the epnymous monsters. This happens because God (i.e. the Writer Herbert Slimmings) decided it would. Herbert decided it would, because the actual God decided that Herbert would decide that. This, if you have faith in some supernatural deity, coincidence is futile and impossible. It would be nice if it were so simple but now I have to pull out the real philosophy and pose the futile and forever unanswerable question that leaves me struggling to sleep at night: How did God come to be? Surely it couldn't have been some sort of...coincidence. Unless He/She/It willed Himself/Herself/Itself into existence, anyway.

This is pretty much as far as this idea can be taken because as stated, there is no answer to the question, or at least not one that can be summised by human law. But it does pretty much go to prove the existence of the two laws in storytelling, be it film, video games, books, music, whatever. There are two rules which create the Law of C: Conflict and Coincidence.
Yeah, I know that I could have used a thesaurus to find some longer words, or come up with some sort of special acronym using other words with the same meaning, but this is how it came to me. For the most part it's simply, but if you spend too long thinking about it, you're going to end up in an asylum...