Definitions aid us in clarifying our concepts and
making them more precise.
Definitions help us know what is and what is
not included in a concept.
We may expand our knowledge by adding new
concepts, based upo
Examples: All geese are birds.
No pelicans are geese.
Some boats are arks.
Some days are diamonds.
All of the above examples are categorical
(The preceding statement is also a categorical
Predicate logic allows us to look more deeply
into the analysis of statements than does
Predicate logic analyzes the subject/predicate
relationship to represent the inner structure
As an example of a sentence in English, lets
The sun is warm.
This example is a statement or proposition
that can be assessed as either true or false.
We can also symbolize the statement, using a
Chapter 7: Categorical Syllogisms
A categorical syllogism is a type of argument
so it is necessary to clearly distinguish the
premises from the conclusion.
Indicator words are helpful in correctly
identifying the conclusion of a categorical
A category is a group of things indicated by a
Classification of things into categories is a key
way of conceptually organizing the world.
Words, particularly nouns, may refer to
categories or groups, which is to say tha
Reasoning with Syllogisms
The rhetorical use of language can distract us from
noticing whether the syllogisms and other
arguments used in the rhetoric are valid and
Identifying categorical, hypothetical, or disjunctive
Sometimes we reason and argue about issues
based on our direct observations or
In other cases, we reason and argue about
issues that go beyond our direct observations
Reasoning with Propositions
Propositions: A proposition can be evaluated
as true or false.
Propositions are the units of thought, and are
typically expressed in sentences.
Sentences involve the subject/predicate
Fallacies are mistakes in reasoning.
There are formal and informal fallacies.
This PowerPoint presentation focuses on the
As you examine fallacies, keep these points in mind:
To decide which f
Truth tables can be used with single
statements and with arguments:
1. The complete truth table shows all the truth
values of an argument, and shows whether
the argument is valid or invalid.
2. The shortcut truth