In the real world, however, this assumption may not be true, because to have a world in first place certain physical laws have to come into play, otherwise it may turn into a total chaos. Yes, our world needs to rely on the laws of physics, on spatiotemporal and other constraints. And it constantly evolves abiding natural rules.
Our biology is similar: we have heredity to fix certain traits and pass them on to descendants in the form of genes and we have natural tools like mutations to be able to change and create new features.
Does the same apply to magic? From the first glance, the answer is no. The great things about fantasy and fiction in general are that you can come up with things that are not real.
But! However magical your world may be you still need to make it believable for your reader. I’ll explain.
Imagine that your protagonist is a powerful witch fighting scores of enemies almost effortlessly coming up with every kind of magic. It is boring. Or she is able to raise anyone from the dead, which means that the worst thing like death is not final. Immortality may be a great thing, but again it is boring. You are less likely to worry about an immortal character, aren’t you? He may be a demigod, but it’s better not making him an eternal invincible god.
Now imagine that the same witch can only use her magic in certain circumstances and can only raise someone from the dead before their brain is decomposed. Better, isn’t it?
Magic is like science, they both need practical limitations simply to be believable and exciting. If you could do anything any moment, you’d have done it already.
So, to make your story great apply some laws and limitations to your imaginary world. The higher the limits the greater the reward; especially when someone manages to go beyond the limits (and that should be believable).
Why introducing the laws of magic/physics may improve your story?
It helps to define the stakes and obstacles for your characters: what they can or cannot do, what they can or cannot sacrifice. These laws affect your characters’ thinking and actions.
It helps to add more detail to your world, make it more colourful. Yes, the colour!
Let’s discuss Jasper Fforde’s Shades of Grey. This sci-fi novel, with elements of dystopia and cyberpunk, captivated me and many others partially because of the constraints of Eddie Russet’s world.
What a wonderful idea this concept of ‘colortocracy’. Imagine people being discriminated on the basis of their colour spectrum perception. What a unique metaphor for our society full of discrimination. And this idea works in part because the characters have to obey or bend the laws of the Colour-ruled world. The conflict is already in the concept.
So are you incorporating interesting laws/constraints into your story? Tell me, I’m very curious.