Logical Thinking · Lesson 2 of 4

Deductive, inductive and analogical reasoning

Ask which kind of reasoning you are doing. Each has a different failure mode and a different check.

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Deductive reasoning moves from general to specific and, when valid, guarantees its conclusion: if all of these contracts require notice and this is one of them, it requires notice. The risk is not the logic; it is a general rule you accepted too easily.

Inductive reasoning moves from specific to general: it worked the last four times, so it will probably work now. It never guarantees anything, and it is most of practical life. The right questions are how many cases, how varied, and what would the exception look like.

Analogical reasoning argues from similarity: this is like that, so treat it the same way. Analogies are how people understand new things quickly, and they smuggle in whatever else was true of the original. Always ask where the analogy stops being true — that boundary is usually where the decision actually lives.

See it happen

"Every client we have taken from that industry has churned. We should stop selling to them."

The read that arrives on its own

Four out of four is a pattern. Stop selling to them.

The same situation, with this idea

This is inductive — a generalisation from cases, so the check is the sample. Four clients, all signed in the same quarter, all handed to the same account manager who has since left. The pattern may not be the industry.

What changed

Naming the kind of reasoning tells you which check applies. A deductive argument is checked for validity; an inductive one is checked for whether the sample could have shown you otherwise.

The takeaway

Ask which kind of reasoning you are doing. Each has a different failure mode and a different check.

Easy to take the wrong way

Treating an analogy as evidence. An analogy shows a possible shape; it establishes nothing until you check whether the parts that made it work are actually present here.

Try this

Find an analogy you use at work. Write down the point at which it stops holding.