Logic in spoken English: Deductive

Are you familiar with logic in English? Using logic well will help you convince people of your opinion and score more highly in speaking tests.  

This is a quick guide to a common type known as deductive logic. That means we start with a general premise then draw a logical conclusion based on it. 

Here is perhaps the most famous 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 put aside the message. Just 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 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 finished 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. It still sounds a bit weird, but it's an improvement.

   I'm from Portland, Oregon. It's a great place. 
   First of all when I think about places to live, good food is the most important. We eat every day, hopefully three times a day, and we should enjoy that time!
   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 speaking 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.


Here is a list of resources to help you communicate logically:

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