PRINCE2 aims to provide a method that can be applied flexibly to a project regardless of factors like scale, type, organisation, geography or culture.
The principles provide this ability by being universal (they are applied to EVERY project), self validating (proven to work over many years) and empowering because they give the users confidence and ability to influence the project.
The principles are based on lessons learnt from past projects both successful and failed and provide a good practise framework, if a project does not adhere to these principles it is not being using PRINCE2 because the principles defines a PRINCE2 project.
It is the adoption of these principles that characterise a PRINCE2 project.