I already talked about reasoning on the individual level, what makes each character do what they do inside a story. Now there is the other side, reasoning on the global scale, or how to create an universe that makes sense.To do that, I usually follow three tips; avoid perfection, avoid hyper magic and pay attention to the hard questions.
Why avoid perfection? Well first because perfection is really hard to sustain, both inside and outside the story, perfection means a complete utopia where every detail of the Universe is in the right place on the right time and the more you dig on it, the more are the chances of you writing yourself into a corner. Secondly because perfection is boring. Seriously true perfection is terrible. Just imagine Superman without kryptonite, immune to magic and everything else and without the Clark Kent side of life. At first glance seems amazing, but when you think about it, it is tedious, dull even. That's why he have weakness. Now you can have a drop of perfection on your tale, like some heavenly place, or some advanced elder race from beyond, that is good, it put things on perspective when you compare the rest of your creation with that drop. Even better if that perfection was lost somehow, because remember, perfection is hard to sustain and definetely not easy to achieve.
Now, about hyper magic, and for the sci-fi lovers among us, Arthur C. Clarke once said that "any sufficiently advanced technology is indistinguishable from magic", so for the sake of this dialogue, lets put hyper magic and hyper adavanced tech in the same bag. "B-but mister Eddie, you are doing a sci fi game aren't you ,with space travel and stuff?" Yes I am and believe me when I say that I'm losing a lot of hair trying to keep everything on check. Lets go with healing magic; healing bruises on an instant without much problem is fine on almost any tale involving magic, while resurrecting people as easily is not. And sometimes not even resurrecting, just growing back limbs, or curing all the diseases. Why? Because when such resource is plentiful or infinite, there is no reason for conflict. Why assassinate in the morning when the target can come back to life before lunch? Why wage war for food, greed and gold when there's plenty of wizards around summoning food and make dirt into gold? And just like the drop of perfection, you can have a drop (but just a drop) of hyper magic. Maybe only one guy can do such wonders and heroes and tyrants do what they can to reach such individual. Maybe the cost to cast one of those mega spells is so high that keeps everyone wondering if it is really worth the trouble (and when I say high, I mean really high, because diamond dust worth of 5000 gold pieces for a true resurrection is still extremely cheap).
If you're still with me, you may have already understood what I mean by paying attention to the hard questions, but even so, lets go for a practical example (I'm really found of them): let's say you created a sci-fi tale where mankind achieved star travel centuries ago. And inside that tale there is a planet where every life form have evolved to kill human beings and, to spice things a little bit, let's say that every night the entire planet freezes for some unknown reason. Now, before you decide to cast your son as the main protagonist of such tale, look at those two questions; WHY and HOW? Why everything on the planet evolved to kill a species that does not exist on the planet anymore? How the did it in the first place? I mean, sure a T-Rex would be one hell of a problem on stone age, middle age and mostly any time period before WW II, but nowdays, with our technology, you can throw dozens of them on any major city of the world and they would be dead in less than a day and the human casualties would still be less than a normal terrorist attack. Now imagine what we as humans could do against such fauna in the future. And if everything freezes and die at night, how they kept evolving? And if evolution was that fast and precise to overthrow mankind, why the local fauna didn't evolve to resist the cold?... So, what I'm trying to explain here is, when creating an universe, please make sure that he makes sense (unless you're creating a magical realm of chaos and distortion, then it's fine, go for it) and for that, my advice is to pay attention to the whys and hows.
Everything I said here are just guidelines that I follow to make my life easier when delivering good projects, but they are not set into stone. You can throw everything I said through the window and still make something awesome. Take Magika for example, it's a tale about wizards with infinite mana, where resurrection spell is easier than a fireball and still they delivered an awesome game. Not a serious one and not really plot driven, but still awesome. So in the end, its all about what you want to deliver and thinking on how you gonna do it.
-Eduardo "Garland" Mello, Lead writer @Young Mind Studio