Chapter 1, Lecture 1
Formal and Informal Logic: An Introduction

Logic is the study of good reasoning. This is our definition, so we'll put it in a box, like so:

Logic is the study of good reasoning.

But this is a huge subject.

 

   Let's see why...

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Formal and Informal

So, let's get a grip by dividing up our subject matter.

We'll be thinking about giving reasons or evidence for some claim we'd like to support or prove. That's logic... such reasoning is called an argument.

An argument is a collection of statements including some (the premises) that are given as reasons for another (a conclusion).

Let's begin with formal logic and arguments that can easily be formalized. Here's an easy example.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The point of all that is that logic is the logic of language. Good formal reasoning will need to have the right structure. That is to say:

A good formal argument has it's sentences put together in the right way.

But there is one more point about the language of arguments. Look back at our definition to see.

An argument is a collection of statements including some (the premises) that are given as reasons for another (a conclusion).

The definition doesn't say "sentences"; it says "statements". What is the difference? Statements are just one type of sentence, a sentence that makes a statement...i.e., says what is true.

To begin to get the idea, click on all of the following that are sentences but do NOT make a statement.

  1. Do you like tea?
  2. I like tea.
  3. Tea...Yum!
  4. Drink your tea.
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pick the three NON-statements

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

OK, let's see if we recall that definition: Logic is the study of...WHAT? Click on the one best answer below.
  1. reasoning.
  2. good reasoning.
  3. formal reasoning.
  4. informal reasoning.