The Toyota Production System is Practice, Not Theory

Pete Abilla from the Shmula blog, recently commented on one of our blog articles Is the Theory of Constraints (TOC) a Theory? He said:

During my short time at Toyota, I learned this lesson well: we were always encouraged to “try and see” — which meant that we should try new ways of doing things to see if they “worked.” At bottom, Lean is quite pragmatic — not axiomatic.

The Importance of Practice Over Theory in the Toyota Production System (TPS)

Taiichi Ohno, the father of the Toyota Production System, emphasized the importance of practice over theory. In his 1973 foreword to the first TPS textbook, he titled it “Practice, Not Theory” (論より実践), emphasizing the need to prioritize practical application over abstract concepts. This idea has been reiterated multiple times in the study of the TPS. He concludes the foreword by saying:

“If you are going to do TPS you must do it all the way. You also need to change the way you think. You also need to change how you look at things.
Just as magicians have their tricks, the gemba technique has its tricks. The magician’s trick in this case is “the relentless elimination of waste”. In order to eliminate waste, you must develop eyes to see waste, and think of how you can eliminate the wastes you see. And we must repeat this process.
Forever and ever, neither tiring nor ceasing.”

Taiichi Ohno’s Thoughts on Theoretical Analysis of Toyota Production System and Its Practical Effects

A decade later, in the foreword to Yasuhiro Monden’s book Toyota Production System published in 1983 by the Institute of Industrial Engineers, Taiichi Ohno states:

“…since the Toyota production system has been created from actual practices in the factories of Toyota, it has a strong feature of emphasizing practical effects, and actual practice and implementation over theoretical analysis. As a result, it was our observation that even in Japan it was difficult for the people of outside companies to understand our system; still less was it possible fo the foreign people to understand it.
This time, however, Professor Monden wrote this book by making good use of his research and teaching experience in the United States. Therefore, we are very interested in how Professor Monden has “theorized” our practice from his academic standpoint and how he has explained it to the foreign people. At the same time, we wish to read and study this book for our own future progress.”

Ohno also wrote in this foreword “Although we have a slight doubt whether our Just-in-time system could be applied to the foreign countries…” due to differences in social and cultural factors, he stated “…we hope and expect that another effective American production system will be created utilizing this book for reference.”

Taiichi Ohno believed that the Toyota Production System was not a theoretical model that could be easily applied in other countries, but rather a set of practices developed through trial and error at Toyota. Ohno passed away before ever visiting Toyota Motor Manufacturing Kentucky (TMMK) or any of Toyota’s factories in the United States. It remains unclear whether Taiichi Ohno’s dream of creating “another effective American production system” has come to fruition.

The Importance of Practice Over Theory in Toyota’s Production System

In the United States, former Toyota Chairman Fujio Cho, who was one of Taiichi Ohno’s most talented students and the executive behind the successful launch of TMMK, said:

“We place the highest value on actual implementation and taking action. There are many things one doesn’t understand and therefore, we ask them why don’t you just go ahead and take action; try to do something? You realize how little you know and you face your own failures and you simply can correct those failures and redo it again and at the second trial you realize another mistake or another thing you didn’t like so you can redo it once again. So by constant improvement, or, should I say, the improvement based on action, one can rise to the higher level of practice and knowledge.”

Cho learned Ohno’s lesson well. But why did Ohno feel so strongly the need to state “practice, not theory“? This may have been due in part to what Professor Satoshi Hino refers to as “An Emphasis on Theory” at Toyota, in chapter 2 of his book Inside the Mind of Toyota: Management Principles for Enduring Growth. Hino writes that Toyota’s leaders including Eiji Toyoda, Shoichiro Toyoda, Hiroshi Okuda, and Fujio Cho:

“…all advocated the theory of an annual production of 200,000 to 300,000 of their basic models, which constitutes the economic production unit, the minimum needed to rep the benefits of the mass production effect.”

Toyota used this “automotive production cost curve” or the Maxcy-Silberston curve, named after the originators, to limit production volumes and instead increase sales and profit through variety. While this is in overall agreement with Taiichi Ohno’s philosophy of the Toyota Production System as “going beyond scale-based production“, this emphasizes that the theory may have represented a threat to Ohno’s vision of the Toyota Production System, born from practice and implementation, not theory.

The importance of practical knowledge at Toyota under Ohno’s leadership

Another reason for Ohno’s emphasis on practice over theory may have been because of a cultural shift at Toyota in the 1970s and 1980s when an increasing number of university-educated young managers like Fujio Cho joined the company. This brought a new emphasis on theories and academic knowledge. If this was the case, Ohno was tough on his subordinates and students such as Fujio Cho for a good purpose, emphasizing learning through practical kaizen rather than theory. There is a famous story of Ohno scolding a subordinate for following his instructions too closely, saying,

“You are a fool if you do just as I say. You are a greater fool if you don’t do as I say. You should think for yourself and come up with better ideas than mine.”

The Importance of Practice Over Theory in Toyota’s Production System

Taiichi Ohno’s emphasis on practice over theory in the Toyota Production System was born from the belief that practical application and implementation were essential to developing effective processes. While there may have been a shift towards more academic knowledge at Toyota, Ohno’s philosophy of continuous improvement through action and kaizen remained central to the company’s culture. The Toyota Production System was not a theoretical model, but rather a set of practices developed through trial and error at Toyota. The emphasis on practice over theory remains a core principle of the Toyota Production System to this day.

 

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