Common sense isn’t necessarily good sense

Dear Bob …

In this week’s Keep the Joint Running (“Iacocca’s alliterative leadership list,” 6/18/2007) you said this about common sense:

Oh, dear. Whether you call it common sense, good instincts, or trusting your gut, the notion is a dangerous one. Too often, “common sense” is nothing more than personal bias, and prevents the very openness to new ideas Iacocca values.

I think you missed the boat on this one. Common sense is not about instinct or trusting your gut. It’s about the ability to tell reality from fantasy. I think that the Clinton quote really speaks to that.

Take something out of one your clients as an example. You talked about how every system has constraints and the constraints affect each other. So, performance, stability and cost are three constraints that have to balance each other. Fantasy tells you that you can have a high speed, high stability system at a great cost. Common sense tells you that, as with most things in the real world, that’s not happening. If you are lucky, you can get two out of the three.

Yes, sometimes your gut gives you common sense answers, but that’s not the point. What is important is the ability to cut through the fluff, whether you do it consciously (better) or not.

– Commonsensical

Dear Commonsensical …

Thanks for making my point for me. Common sense told you that you can’t get a system with high speed, strong stability and a low price. Your common sense is wrong, because you can.

All you have to do is to sacrifice on features and functionality, and accept only limited scalability. Also, when deciding on “speed” you might have to choose between a system that delivers fast response time and another that delivers high throughput rates, instead of getting both.

None of us is born with an understanding of systems optimization. I’m willing to bet you didn’t figure out “quicker, cheaper, better – pick two” on your own. I’m pretty sure someone explained it to you early in your career. You learned it and made it part of your worldview.

Calling book learning “common sense” is a peculiar use of the term.

One reason I’m confident you didn’t figure this out on your own is that had you done so you’d have figured out that quicker, cheaper, and better each consist of two separate and independent parameters – the other three optimization dimensions I offered above.

For a quick tutorial on the subject, here are three KJR’s that cover the ground: “Quicker isn’t as simple as it looks,” (5/19/2003) “Of costs and thermostats,” (5/26/2003), and “Quality matters. How you define quality matters even more,” (6/7/2003).

I know this approach is important because I once watched a process re-engineering effort severely damage a company through a dramatic improvement in cycle time (throughput, sadly went through the floor). I know it isn’t common sense because I know professional process re-engineering consultants (and one former physicist) who haven’t yet built it into their thought processes.

A friend pointed out to me that there is a valid use for “common sense” – situations like driving in the rain and recognizing that slowing down and turning on your windshield wipers might be a good thought.

Yup. Just like they taught us in Driver’s Education.

Last nail in the coffin: Imagine someone whirling a ball on a string above their head. They let go of the string. Describe the ball’s horizontal trajectory.

Even in this day and age, many expect the ball to follow a curved path. Three centuries ago, Newton gave the world the correct answer with his three laws of motion.

Many of those who know the right answer will explain that it’s just common sense.

So will those who don’t. The funny thing is, those who don’t are the ones who really are using their common sense.

Those who are right are making use of what they studied in school.

– Bob

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