No theory forbids me to say "Ah!" or "Ugh!", but it forbids me the bogus theorization of my "Ah!" and "Ugh!" - the value judgments. - Theodor Julius Geiger (1960)

Most people, when asked where they know Deming from, say "Plan-Do-Check-Act". That's not exactly right, though. The original Shewhart cycle and Deming wheel were translated into Plan-Do-Check-Act in Japan, but Deming described it as the Shewhart Cycle for learning and improvement: Plan-Do-Study-Act. While PDCA is used for implementation and compliance, PDSA is used for testing and implementing (Moen and Norman, 2009).

System of Profound Knowledge
In the late 1980s and the early 1990s, Deming initiated a revolution in management theory. His holistic approach provides leaders with tools to transform their organizations into systemically focused entities that thrive in our dynamic and complex world.

Deming's System of Profound Knowledge (Deming, 1993) is like a practical guide for management. It helps you to address the often more deeply rooted issues in your organization so you can lay the groundwork for real change and continuous improvement.

It all starts with a personal transformation: understand the principles, apply them in your daily interactions and become the driving force behind change within your organization.

The System of Profound Knowledge consists of four essential, interrelated areas:
1. Appreciation for a system: Think of your organization as a big web, where everything is connected. Each part affects the whole. It's about seeing the organization as a whole, not as individual parts. This way you get a better idea of the big picture by which you can optimize processes and achieve synergy.
2. Knowledge of variation: Understanding the variations in your system(s) will help you address problems and eliminate barriers within the system(s). It's about knowing what's normal (common cause) and what's not (special cause). In that way, you can also try to predict and prevent problems.
3. Theory of Knowledge: Challenge yourself to continuous learning. Challenge assumptions, participate in experiments, and make predictions to deepen your understanding and make better decisions. It's about breaking the illusion of knowledge and gaining a deeper understanding of your beliefs.
4. Psychology: Understand the power of human nature in the organization. Create an environment where people can grow, take pride in their work and develop their talents. It's about removing fear, boosting motivation, and fostering collaboration. The psychological effect is almost certainly the most complex part to work on.

Whether you're leading a small team or a large company, Deming's principles are a great guide to help you on the path of continuous improvement.

Deming, W.E. (1993), The New Economics, MIT Press.
Moen, R., Norman, C. (2009), The History of the PDCA Cycle, in: Proceedings of the 7th ANQ Congress, Tokyo 2009.