PHIL 210 Course Outline

PHIL 210 Course Outline
Lesson 1
What is a statement?
 A statement is also known as a proposition, sentence, or claim
 A statement is anything that can either be true or false
 For example: "Dave is tall" is a statement but "Dave, pass the salt" is not a statement
Note: Ask yourself if the statement can be true in some circumstances and false in other circumstances
Note: An assertion is the act of stating something as if it were true.
What is a premise?
A statement intended to provide rational support for some other statement (a conclusion), often in conjunction
with other premises.
What is a conclusion?
A statement intended to be rationally supported by a set of premises.
What is an argument?
 A collection of premises that justify, or are supposed to justify, a conclusion.
What does validity mean?

 A structural property of an argument
 An argument is valid if there is no way for the conclusion to be false if all the premises are true.
 For example:
o "If Stephen Harper is a fish, then he spends his life under water"
o "He is a fish"
o "So he spends his life under water"
Note: We are not concerned about whether the premises and the conclusion are true, but whether it is possible
for the premises to be true when the conclusion is false. In the example above, the premises imply that the
conclusion is valid.
What is soundness?
 An argument is said to be sound if it meets two conditions: the premises are true and the argument is valid.
 For example: "Stephen Harper is a fish" is not a true statement. Therefore, the argument is not sound.
What is inference?
Inference is the act of reaching a conclusion on the basis of some premises
What are the different types of arguments?
 Linked: The premises interrelate in order to form a single case for the conclusion
 Sequential: The argument contains one or more sub-conclusions that in turn function as premises for the
overall conclusion
 Convergent: The premises provide multiple distinct lines of support for the conclusion
Note: Validity and soundness apply to arguments; truth and falsehood apply to statements; premises imply a
conclusion; people infer a statement.
What does it mean to be logical?

 Does not mean being sensible.
 Logic in general is the study of methods of right reason.
 Logic in particular is a set of inference rules which are described as the "Laws of Thought":
o The Law of Identity: P if an only if P {each thing is identical with itself}
o The Law of Non-Contradiction: Not both P and not-P {contradictory propositions cannot both be
true in the same sense at the same time}
o Law of Excluded Middle: P or not-P{ for any proposition, either that proposition is true or its
negation is true}
What is a compound statement?

Compound statements are statements using two or more sentences joined together.
What are the different types of compound statements?

1) Conjunctive statement (conjunction):
o A compound statement containing two sub-statements (called conjuncts), joined with the word ‘and’,
or near-synonyms like ‘as well as'.
o A conjunction is true if and only if all of its conjuncts are true
2) Disjunctive statement, or disjunction:
o A compound statement containing two sub-statements (called disjuncts), joined with the word ‘or’, or
near-equivalents like ‘alternatively
o A disjunction is true if and only if at least one of its disjuncts is true.
o Disjunctive statements can be either inclusive or exclusive:
 Inclusive ‘or’: at least one of the listed disjuncts is true. (Hence the inclusive disjunction is
also true if both its disjuncts are true.)
 Exclusive ‘or’: one and only one of the disjuncts is true.
Note: It is easier for a disjunctive statement to be true than for a conjunctive statement. A disjunctive statement
is true provided any of its disjuncts are true, while a conjunctive statement is true provided all of its conjuncts
are true.
What are some valid disjunctive argument forms?
Disjunctive Syllogism Constructive Dillema
1. P or Q 1. P or Q
2. Not Q 2. If P then R
Therefore, 3. If Q then S
3. P Therefore,
4. R or S

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PHIL 210 Course Outline

What does validity mean?

What does it mean to be logical?

What is a compound statement?

What are the different types of compound statements?

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