Logic in spoken English: Inductive

This post is about inductive logic: starting at a specific point and generalizing out from it. This builds on the previous post about deductive logic, so if you haven't read it, or you don't remember it, take a look now before you go on.

Logic is important in spoken English. It helps us convince our friends of something, sell products to clients, and score highly on English language speaking tests. This post will look at inductive logic. Let's take a look at a simple example: 

A) This morning the weather is clear. 
B) Most sunny days start with a clear morning. 
C) So, most likely, today will be sunny. 

You can see we start with a specific example and work out a conclusion based on it. Is the conclusion reasonable? In this case, yes.

Let's look at another example: 

A) I went to Paris. 
B) Every person I met there was so friendly! 
C) So, I think all the people in Paris are friendly.

This is not a valid conclusion. If you have been to Paris, you may have found that it lives up to its reputation as an unfriendly city. So, we can see the weakness of inductive arguments. 

However, most scientific studies use inductive reasoning. Scientists study specifics, and they do it enough times to be able to generalize. The tough questions are: 

  • how many specifics do we need; and
  • what percentage of them have to support our conclusion?

Most scientists agree that a sample of at least 50, with 95% in support, is good enough. Your friends, clients or speaking test assessors probably won't be strict about it, but it's good to keep those numbers in mind. 

So, let's make the Paris argument stronger. Let's also use spoken English: 

The best place I've been is definitely Paris. Every person I met there was lovely, from shop staff to tour guides, to other travelers. Maybe I was just lucky, but I met dozens of people and every single one was great. So, you should go to Paris and chat with the locals. I can't promise, but I bet you'll meet some really lovely people. 

This has enough specific cases (dozens), and a high enough percentage of successes (every single one). 

Now that we know the guidelines for inductive reasoning, let's go back to the weather example and make it stronger. 

(A) This morning the weather is clear. (B) I've noticed over the past few months that every day that started with clear weather had clear weather all day. (C) So, I'm pretty confident that today is going to be a nice day. 

There is enough data with a high enough percentage of success. You should also notice, however, that the conclusion is not completely sure

Inductive reasoning can only give us a good idea about what will happen. We can be pretty confident, or you can bet on the result. We can't be fully confident, though. 

Try it now. Here's a question to help you start:Is your company a good place to work? 


If you have any questions or would like to practice this skill, you can ask your teacher in your next English class.