The central conceit is that when we disagree about how to get something done, or how something should work, or how we should coordinate and collaborate, we typically get stuck because we’re thinking at the level of the bottom of the spine - Practices and Tools - where many preferences and subjective truths exist.
The Spine Model’s core idea is that we should move up the spine and think in terms of Needs, Values and Principles first, find agreement there, and then build on that agreement to create suitable Practices, and then to identify suitable Tools to support those Practices.