Principles can carry the intent from the theory they represent. Military strategy has a long history of being presented through principles of war. In Lean Construction, principles like “flow,” “pull,” “remove waste” are used with ease. However, have they been correctly treated and understood? Supported by a literature review, we follow the use of principles through the history and the standing and character they have gained. The work is grounded in the important position of principles between theory and practice, and methodologically proceeds through philosophical conceptualisation. We recognise the guiding, dynamic, adjustable, durable, action-oriented, prescriptive and descriptive capabilities of principles, and emphasise their important capacity to facilitate abductive reasoning. We call for reflection upon the power of principles to strengthen the theoretical conceptualisation of Lean as well as upon their power to support improvement in practice.