Principles are general truths or propositions that could have numerous ways of being applied. They describe dynamics of how work works in an particular environment. They are commonly expressed as heuristics that provide boundaries within which concrete practices are applied.
When applying the Spine Model, you need understand which Principles are important in your context so that you make sure you can use them to your advantage. You do this by looking at the Values. You also need to be able to uncover and debate the Principles on which other people are basing their assumptions.
Principles are those things behind the Practices. Every Practice comes into existence because it tries to express a set of Principles. We think of Principles as a set of “ecological levers” - switches and dials that you believe you can use to effect a desired change to a system. You can do this by establishing governing heuristics for Principles, which then guide people and can be used as a measurement of adherence.
Unlike Practices, Principles are often fractal in nature, applying equally at various levels of the system. For example, Principles around batch size are typically equally applicable to an individual, an organsation and even an industry. We know that if you increase batch size you delay feedback. If you reduce batch size you increase feedback. This Principle remains true regardless of the context or scale of the human work system.
Useful systemic principles can be extracted from many different schools of thought - Queuing Theory, Complexity Science and Theory of Constraints to name just three.
For some examples of Principles, see the Principles Catalogue.