Deductive, inductive and Abductive reasoning

Being effective, you need to be able to influence others to see your point of view. Understanding the different forms of structuring arguments can help you make a clearer case to those that matter.

(credit Pexels)

Thinking…

In a conversation at work recently we got to talking about different ways of presenting arguments. Coming up in the conversation were the options of deductive, inductive and abductive reasoning. I am no lawyer (if I was I guess I would know all about it already?!) but this seemed like an interesting topic to explore further.

Barbara Minto talks about the inductive and deductive forms of reasoning in her book “The Minto Pyramid” (p17)

A deductive grouping ,presents an argument in successive steps. That is, the first idea makes a statement about a situation that exists in the world today. The second idea comments on the subject or the predicate of that statement, and the third idea states the implication of those two situations existing in the world at the same time. Thus, the grouping would have the following form:

Men are mortal (A -> B)

Socrates is a man (C = B)

Therefore Socrates is mortal ( therefore C = A)

An inductive grouping by contrast, wiIl take a set of ideas that are related simply by virtue of the fact that you can describe them all by the same plural noun (reasons for, reasons against, steps, problems, etc.). The form of this argument would be:

French tanks are at the Polish Border

German tanks are at the Polish border.

Russian tanks are at the Polish border.

Therefore Poland is about to be invaded by tanks

As engineers we like details and working through problems we typical would use a deductive approach to understand the root cause and lead us to solutions. Our inclination is to then present the findings back to anyone that is interested in an deductive manner

“I did this, which led to that, from which we then found out this which finally led us to uncover this terrific idea which we recommend”

Although it it logical to present back your work in this manner — especially when you have the background of how you got there, the audience are generally much more interested and you will have far more impact if you present the information in an inductive manner -

“This is what we found and this is why it makes sense to implement it”.

You can always go into the detail further into the presentation if your audience remains interested or requires additional details or convincing.

Deductive reasoning

Inductive reasoning

John Eaton writes in his article “Using Inductive Thinking to Communicate Strategically” about the benefits of inductively presenting your communications:

There’s usually also a huge backlog of information and decisions needing to be made from multiple sources, vying for time and attention. Using inductive principles, you can best apply your thoughts to appeal the most efficiently to people who make decisions that are saddled with too much information. You open your communication with both a summary of the problem or opportunity, and a definitive solution.

This technique is also sometimes called “Answer First” — instead of building to a conclusion you state the problem and solution first, then use the rest of the information to build your case(s). This all starts with a hypothesis as “the answer” and to support your decision, you should focus on two questions: What is it? (Hypothesis) and Why should you do it?

You then apply a controlling structure in everything you communicate to reinforce your supporting ideas, justify your decisions and get buy-in to what you are asking to be done. An effective structure involves two aspects and two key benefits:

1. Arranges ideas into distinct, logical groups so it’s easier for the reader/viewer to absorb and remember the information
2. Putts emphasis on the supporting logic so the reader/viewer arrives at the conclusion you intend.
3. Serves as a roadmap for analysis to help you drive toward a finished product
4. Enables syndication of the story prior to analysis to allow you to get that coveted “buy-in” so you can make changes easily — the fail early and often scenario.

The Pyramid Principle of inductive reasoning — John Eaton

Barbara Minto does highlight the one time you want to present your argument deductively is when you are presenting an argument that you think might be totally unexpected or foreign to the audience. This way you can work up to the proposed solution and bring the audience along, so there is not as much dissonance when you finally get to the proposed solution.

Finally we get to the third type of reasoning — Abductive reasoning

Abductive reasoning typically begins with an incomplete set of observations and proceeds to the likeliest possible explanation for the set. Abductive reasoning yields the kind of daily decision-making that does its best with the information at hand, which often is incomplete.

A medical diagnosis is an application of abductive reasoning: given this set of symptoms, what is the diagnosis that would best explain most of them?

Butte College: Deductive, Inductive and Abductive Reasoning

Being effective, you to be able to influence others to your point of view. Understanding the different forms of structuring your arguments will help you make a clearer case for those that matter to see the world your way.

Further Reading

• Barbara Minto — The Minto Pyramid
• Stony Brook University: Scientific Reasoning
• John Eaton “Using Inductive Thinking to Communicate Strategically”
• Butte College: Deductive, Inductive and Abductive Reasoning
• Stanford Encyclopedia of Philosophy: Abduction
• Model-Based Reasoning in Science and Technology
• Scientific American: Your Scientific Reasoning Is More Flawed Than You Think

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