Logic in spoken English: Deductive

Using logic in English is easy, but often we forget to use it. This is a quick guide to a common type of logic that will help you convince people of your opinion and score more highly in speaking tests like the G.B.C. that require a logical answer.  

Let's look at traditional deductive logic. That means we start with a general premise, then draw a logical conclusion based on it. 

Here is perhaps the most commonly used example: 

Major premise: All humans are mortal.
Minor premise: Socrates is human.
Conclusion: Socrates is mortal.

You can also follow this line of reasoning for many other topics: 

Safe cities are good to live in.
Tokyo is a safe city.
Therefore, Tokyo is a good city to live in. 

It's useful to think about logic aside from message. Think about it like math: A = C, and B = A, so B = C. Put another way:

  • safe = good,
  • and Tokyo = safe,
  • so Tokyo = good. 

Deductive reasoning is the technical name for this type of logic. It starts with the major premise, then adds a minor premise that defines your argument, and then reaches the correct conclusion based on those two premises. 

This is simple, but a lot of students miss it when they are speaking. For instance: 

My hometown is a great place to live.
There are a lot of great restaurants and the people are friendly. 

That example is not a logical argument. It's missing a linking step. 

Here is that argument, done logically: 

My hometown is a great place to live.
I think good food makes for a good place. 
My hometown has some really good food. 
Therefore, my hometown is great. 

You can see, if we write it like math, it works: (a) good food = (b) a good place; and (c) my hometown = (a) good food; then (c) my hometown = (b) a good place. 

Although that was a logical answer, it's a bit weird in spoken English. It needs detailed evidence. Here's the same logic with some detail, in spoken English: 

   I'm from Portland, Oregon. It's a great place. 
   First of all, we can all agree good food is important. We eat every day, hopefully three times a day, and we should enjoy that time! So I think good food makes for a good place. 
   Portland has the best food. There are so many great restaurants. The ingredients are local and fresh, and the flavors are a mix of different cultures, like Mexican, Chinese, American, and more. It's all done so well. You have to go and taste it for yourself. 
   So, since good food makes for a good place, and Portland has the best food—obviously, it's a good place to live!  

If you want to convince people of your opinion and get a high score in your next G.B.C. test, then practice making your logic plain and clear.

Try this now. Here's a question to help you start:

Where would you recommend a tourist visit in your country?

Think about what is important for travelers. Think about what makes for a good place. Then use deductive reasoning in your answer.

This topic ties into The English Farm's Speaking Test Strategies course's lessons on reasoning: lesson 4 adding reasoning, lesson 13 layering reasoning, and lesson 18 roll-on effects.  

Be sure to read the following post on G.B.C. sample answers using deductive reasoning.

If you have any questions or issues with this topic, you can discuss them with your teacher in your next English class.