spine, to put it bluntly, begins with  your first strong idea. you were scratching to come up with an idea, you found one, and through the next stages of creative thinking you nurtured it into the spine of your creation. the idea is the toehold that gets you started. the spine is a statement you make to yourself outlining your intentions for the work. you intend to tell a story. you intend to explore this theme. you intend to employ structure.

[…]

the spine is my little secret. it keeps me on message, but it is not the message itself.

[…]

you might not see your work this way. you might struggle for spine. you  might be content to receive any random thought floating through the ether that happens to settle on you that day. you might think you don’t need a supporting mechanism for the art you’re constructing, a controlling image, a collateral idea to guide you. you might think getting lost is a big part of the adventure.

you may think that, but you’d be wrong.

[…]

keep in mind that coming up with a spine is neither a chore nor a distraction that takes you away from the real work of the creative process. it is a tool, a gift you give yourself to make your job easier.

twyla tharp on the creative habit |via texturism |photo via mociun [emphasis mine]