Aristotle is credited as the first to say, “The whole is greater than the sum of its parts.” In other words, if you have the ingredients you’d use to bake a pie in a pile, it isn’t as meaningful as having the baked pie itself. The value of the final product isn’t just about gathering the raw materials; knowing how to properly mix the ingredients in the correct order with the right timing and presentation are all part of the recipe too. But as examples go, baking a pie might seem a bit simplistic. Imagine instead the thousands of parts and components that go into building a car. How difficult would it be to put them all together to form something that actually drives down the road? How about all the parts to build an airplane that actually soar above the clouds? Or all the components to build an aircraft carrier that can sail the seven seas instead of sinking to the bottom? The pie is probably sounding a lot easier now. But what if you were attempting to make a lot of pies — enough to stock every supermarket from San Diego to the tip of Maine? How do you manage that kind of load? One strategy extracts more value from the parts that make up the whole: production line modularity.

To be clear, the whole is still greater than the sum of the parts on the production line, but if a manufacturer can gain greater control of those parts, great power can be extracted. Modularity, in its essence, is the subdivision of a system into smaller parts. Each of those parts is called a module. Each module can be modified, replaced, or exchanged with other modules to make changes, even improvements, to the system it serves.

Now think of a mechanical watch. Every gear, spring, and wheel serves an extremely precise purpose that ensures time is kept accurately, not a nanosecond off. Change just one sprocket and not only would you have to pause time (or just the watch), but the slightest component change would alter the whole — seconds could take a fraction longer to tic, eventually knocking minutes, hours, and days off kilter. A mechanical watch is not a modular design.