Friends, Romans, countrymen, lend me your ears; I come to bury Caesar, not to praise him. The evil that men do lives after them; The good is oft interred with their bones; So let it be with Caesar.

That's from an eulogy Mark Antony delivers in Shakespeare's Julius Caesar. You may not have the entire play committed to memory, but very likely you have previously heard and retained the first three words of that eulogy. Something about the number three helps us organize, retain and communicate information effectively. We can see examples of this in how the Toyota Production System has been encoded as well, in what we'll call the "Lean Enterprise Rules of Three." Let's examine these in the three lean areas of purpose, process and problem solving.

1. The Purpose of Lean

Like any good system of continuous improvement, Lean should be used to nurture people, profit and the planet (let's expand our thinking off-planet after we confirm that our impact beyond it is significant). This is sometimes called the "triple bottom line." Lean achieves the triple bottom line by measuring and improving performance in each area of the "three elements of demand." They are quality, cost and delivery. Safety is often added to the front of this to humanize the workplace, but one could argue that safety is implied in both quality and cost.

The Toyota way teaches us to define value from the point of view of the customer (asking "is this good for people, profit or the planet?") and focus our on getting rid of all mura, muri, muda in all processes. In other words identify, isolate and eliminate variability (mura), overburden (muri) and waste (muda) systematically.

2. The Process of Lean

A good way to get started with this is through a sustained practice of 5S, which is really just sort, straighten and sweep with two more S added to keep up the first three. This is a lot easier to do when you have thoroughly understood the aim of 5S, which is to make waste, overburden and variability immediately visible.

Lean also teaches us to organize our work in a way that minimizes waste and also exposes hidden problems or "reasons why this won't work." One of the pillars of the Toyota Production System is the idea of just in time, or doing what you need, when you need, in the amount you need. This is done by calculating the daily takt time and balancing your work to this pace, working on one piece at a time in a flow, and letting the downstream pull of the next process be the signal to start work. Just in time will both minimize waste and expose problems or weaknesses in your system very rapidly.

The definition of standard work comes to us in a rule of three, being "the most effective combination of manpower, material and machinery." The three elements of standard work are takt time, work sequence, and standard work in process (SWIP). Once you have standard work, or any sort of basic standards, you have a basis for the next improvement.

3. Problem Solving in Lean

Lean sees any deviation from the standard as an abnormality, which is an opportunity for improvement. The spirit of jidoka, the practice of giving machines and processes human intelligence to build in quality, can be summarized as stop, call and fix.

All problem solving should be done by following the practice of genchi, genbutsu, genjitsu or going to the site, checking the actual item and getting the facts. This is sometimes shortened to genchi genbutsu or simply "go see" in English.

Plan, Do, Check Act is a 4-step cycle but most people miss the third step - check. Taiichi Ohno said "Check is hansei" and I believe that the correct practice of PDCA is 1) Plan, 2) Do and 3) Hansei. Hansei implies reflection on past actions and a plan to adjust future actions. Perhaps it's not "ready, aim, fire" bur rather "aim, fire, ready."

Lean is a never-ending process, ultimately about the pursuit of perfection, which can be summarized in a rule of three also: practice, practice, practice.

Can you think of other lean enterprise rules of three? What's your favorite rule of three, in life or in lean?