2. Inductive Arguments and Strong Reasoning

2. Inductive Arguments and Strong Reasoning

In logic there’s a close relationship between deductive and valid arguments, and there’s a similar relationship between inductive and strong arguments.

In standard logic, the term “inductive argument” basically means “an argument that is intended to be strong rather than valid”.

So, when you give an inductive argument for a conclusion, you’re not intending it to be read as valid. You’re acknowledging that the conclusion doesn’t follow with certainty from the premises, but you think the inference is strong, that the conclusion is very likely true, given the premises.

Here’s an example of a strong argument:

1. Most Chinese people have dark hair.
2. Julie is Chinese.
Therefore, Julie has dark hair.

We would call this an inductive argument because it’s obvious that the argument is intended to be strong, not valid. Since the argument is in fact strong, it counts as a successful inductive argument.

And as with deductive arguments, we also want to be able to talk about FAILED inductive arguments, arguments that are intended to be strong but are in fact weak.

Like this one:

1. Most Chinese people have dark hair.
2. Julie has dark hair.
Therefore, Julie is Chinese.

Here we’re supposed to infer that, simply because Julie has dark hair, she’s probably Chinese. This is a weak argument.

But we still want to call it an inductive argument if the intention was for it to be strong. In this case the word “most” indicates that the inference is intended to be strong rather than valid. We would call this a WEAK inductive argument.

So the terms “strong” and “inductive” have a relationship similar to the terms “valid” and “deductive”.

• To call an argument STRONG is to say something about the logical properties of the argument itself (that if the premises are true, the conclusion is very likely true).
• To call an argument INDUCTIVE is to say something about the INTENTIONS of the arguer (that the argument is intended to be strong).