Chapter Eight Logical

Remember the irritatingly left-brained “Mr. Spock” from Star Trek? I assure you, he’s not usually the kind of person you want on a creative design team. Yet this chapter is all about being logical and rational. It’s about using common sense and reason to figure something out—or help design something someone else needs to figure out. You actually do need to adopt a stern demeanor for a lot of what’s going to follow. And be prepared to take some grief from your designer(s)—they’re going to tell you that you are stifling their creativity. No, you’re just making sure they continue to create elegantly clear solutions.

Three basic types of logical reasoning

Here’s some background on how logical reasoning works that you might find helpful. Feel free to skip the next couple of paragraphs.

In very general terms, there are three types of reasoning:

Deductive reasoning is how we arrive at the “truth”—whatever that may be. It means that if A = B and B = C, then A = C. There is often something sequential about deductive reasoning, which I get to a little later in the chapter.

Inductive reasoning isn’t necessarily true, but suggests the probability of something being true. It helps us make a judgment based on past observations: “Joe has been driving for 40 years. He has never had an accident and only one ticket. Therefore, Joe must be a good driver.” What we don’t know is how much driving Joe actually does. Maybe he walks or bikes most of the time. But the probability ...

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