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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.

The Last Planner System (LPS) is a tool for project planning and control, and is an important contribution from Lean Construction. LPS focuses on scheduling, task coordination and time management. Uncertainty Management (UM) is a key element in Project Management, where uncertainty is the totality of opportunities (potential upsides) and risks (potential downsides). UM addresses all types of uncertainty (related to cost, time, quality, scope, safety, customer satisfaction, company reputation, etc.). The aim of UM is to exploit the opportunities and reduce the risks.Two construction companies involved in this research are working with both LPS and UM. One has extensive experience with LPS, but less experience with UM. The other has extensive experience with UM, but less experience with LPS. Two questions are raised and discussed in the paper: 1. Could project planning and control be improved by an integration of LPS and UM? 2. If yes, how could LPS and UM be integrated to improve project planning and control?The paper proposes a conceptual model where UM tools are integrated in the plan and meeting structure of LPS. The model is to be tested in forthcoming case studies.

A paradigm shift occurred in economics in the middle of the 20 th century. According to the old paradigm, economics studies the determinants of wealth. The new paradigm, called neoclassical economics, posits that economics studies behaviour under scarcity of resources. A corollary of the new view is that people and organisations can be assumed to make optimal, best possible, decisions regarding the scarce resources.The old paradigm of economics recognized waste as a factor influencing wealth. The new paradigm, focusing on optimal allocation of resources, did not apply the notion of waste. The Nobel laureate economist Stigler went in 1976 even further and claimed that waste is not a useful concept in economic theory, though he admitted the occurrence of waste, which he narrowly defined as a foregone product that can be obtained for less than its cost.The 1976 paper of Stigler is critically assessed. Three major shortcomings are found. First, waste is ubiquitous in economic activities, whereas Stigler downplayed its significance. Second, waste can occur irrespective of the context, whereas Stigler insisted that waste occurs in the context of market exchange. Third, decision usually needs to be implemented in the material world, and waste often emerges in this implementation. Stigler considered decisions without taking implementation into account.To rectify the shortcomings in the economic conception of behaviour under scarcity, a new conception is offered. It is based on the recognition of three different types of waste in relation to a decision: background waste, non-optimality of the decision, and foreground waste. There should be an attempt to reduce or to eliminate all three types of waste. The new conception implies that the starting point of neoclassical economics has been seriously wrong.