By Jon Miller | Post Date: August 18, 2007 10:52 PM | Comments: 10
The tag line Theory of Constraints Exposed in IndustryWeek article from March of this year got me thinking about TOC. Not a bad article by the way, although I'm still waiting for the Lean-TOC software system sales pitch shoe to drop.
It got me thinking, is Theory of Constraints really a theory? By theory I mean scientific theory, since any efforts toward improvement should be scientific, in my opinion. The glossary at What is Life tells us:
A scientific theory is an established and experimentally verified fact or collection of facts about the world. Unlike the everyday use of the word theory, it is not an unproved idea, or just some theoretical speculation. The latter meaning of a 'theory' in science is called a hypothesis.
So is TOC a scientific theory, a theory in the latter sense in that it is a hypothesis that can be proven or disproved, or neither?
If it is neither, we are at risk of practicing something akin to "belief" as a management and improvement system by using TOC, which is a thing fraught with risk. If so, perhaps it should be called DOC - Dogma of Constraints.
In the philosophy of science there is something called "falsifiability" which is extremely important. Falsifiability is logical quality of empirical statements such that they allow for logical counterexamples. Stated simply, a scientific theory must be falsifiable - there is a way that it can be proven wrong. In contrast, formal and mathematical statements can be universally true by definitions, axioms or proofs. These are more like tautologies.
Although management and improvement systems such as the Theory of Constraints or the Toyota Production System can and do contain mathematical statements or formulas which fall into this latter category, as theories or operating models, they must be scientific in order to be testable and therefore practically applicable.
The philosopher Karl Popper taught that no empirical hypothesis, proposition, or theory can be considered scientific if it not falsifiable. It must admit the possibility of a contrary case. We don't need to observe or demonstrate that a theory is false, merely that it is logically possible for the theory to be false.
A good way to test for unfalsifiability (or untestability) is to show that a particular theory does not make a prediction, or that the predictions it makes cannot ever be wrong, even if the theory is false. It is then unfalsifiable, and therefore not scientific.
An example that is often given is that a divine being created everything that exists. While this may be true, it is not scientific by the above definition, since there can be no possibility of evidence to the contrary. Under divine creation as a scientific theory, if we did find evidence that would contradict it, according to the theory that evidence was also divinely created. There is no logical possibility in this theory that it could be false.
Is Lean a scientific theory? As a management system, Lean is scientific in terms of the thinking process. Lean has been experimentally verified in many cases over decades. The theoretical premise, or basic hypothesis of Lean, can be stated as:
1. The customer defines value by what they are willing to pay for
Waste is specifically defined in the seven types (overproduction, transportation, motion, inventory, defects, waiting, processing) as well as safety losses, wasted space, energy losses and environmental harm. If reducing inventory, defects or motion did not in fact reduce cost, then this theory could be proven false.
It is worth noting that Taiichi Ohno, the person who is credited with developing and advancing much of what is known today as Lean management, often spoke out against TPS being a theory of any kind. The words "practice, not theory" or "practical, not theoretical" were his rejoinder to managers and professors alike who poked and prodded at the workings of TPS. So perhaps "is Lean a scientific theory?" is the wrong question.
Lean appears to pass the test of falsifiability. But what about the Theory of Constraints? The steps to managing through the Theory of Constraints are:
0. Identify the goal (that which is being constrained)
My concern here is that it appears to say in step 5 is "if the Theory proves false, repeat the test until it is proven true". Does TOC admit the possibility that identifying and exploiting the constraint and then subordinating all other to the constraint, and elevating the constraint will fail to achieve the goal?
Is the Theory of Constraints falsifiable? Is it useful for making predictions? Is the Theory of Constraints a theory, or in fact a belief? You TOC experts will need to speak up to answer this question.
Even if not a theory, TOC remains useful, but we need to be careful what we call things.Comments are moderated to filter spam and inappropriate content. There may be a delay before your comment is published.