1.3 Logic and Form
There are many ways to study logic. The way we take in this book is called formal or symbolic logic because we will study the form of reasoning and inferences.
Form: a structure or pattern.
The form of something is its structure, a repeatable pattern. For example, consider a form used to make something out of cement or concrete: you can reuse the form to make many objects that have the same shape.
Sentences, arguments, and rules of reasoning all have form.
This is easiest to see with an example. Here's a form we can reuse to make sentences that share a structure:
If ___ didn't bring an umbrella, then ___ is going to be wet.
We insert a name in the gaps, sort of like pouring concrete into a form, in order to build a sentence:
If Pia didn't bring an umbrella, then Pia is going to be wet.
Then we can reuse that form to make another sentence with the same structure.
If Quinn didn't bring an umbrella, then Quinn is going to be wet.
In order to make it clear that the same name has to go into both gaps, we put a symbol there. For example,
If X didn't bring an umbrella, then X is going to be wet.
Replacing words with symbols is how we reveal the form of a sentence. Let's practice.