Reasoning: An Introduction to Logic, Sets, and Functions
Two key differences between predicate logic and Boolean logic are:
- In Boolean logic, our building blocks were complete logical statements. For example, we gave the name W to the claim, “The sidewalks are wet.” In predicate logic, we’ll start with objects, like Smokey, and then build up our claims about them.
- In Boolean logic there was no way to generalize and make a single claim about many different objects (except by explicitly conjoining statements about each of them as individuals). In predicate logic, the quantifiers ∀ and ∃ will let us make such general claims in a single statement.
Now we’re ready to start with the building blocks of predicate logic. We’ll use:
- drawn from our universe of discourse.
- that may take on as their values any of the objects that we can talk about.
- that apply to objects and return objects.
- , which are a special kind of function. A predicate must return a Boolean value (i.e., T or F). The job of objects and functions is to provide fodder to predicates. Predicates enable us to build logical expressions that we can reason with.
Exercises Exercises
1 .
1. Consider the wff:
Complete each of these statements:
Meat is a(n): object
Sausage is a(n): object