Philosophy 103Linguistics 103

Introductory Logic: Critical Thinking

Fall 2007

Dr. Robert Barnard

Syllabus Basics (1)

• Textbook:

Patrick Hurley – Concise Introduction to Logic (9th Ed)

• Homework and Online Quizzes:

Thomson Now/ iLrn at – www.ilrn.com

• Syllabus details

http://home.olemiss.edu/~rwbjr/rbphil103.htm

Syllabus Basics (2)

• Attendance and Participation (100 points)

• Homework (200 points)

• 4 Quizzes (200 points total)

• 2 Mid-term Exams (300 points total)

• 1 Final Exam (200 points)

PHIL 103 Grading Scale

890-1000 = A

780-889 = B

640-779 = C

500-639 = D

000-499 = F

• No Final Exam Option:Pre-Final A (720 +) or Pre-Final B (640-719) may opt out of final exam.

• Comprehensive Final: Any person who a) takes the final and b) passes the final at 80% or better will pass the course with a course grade of C or better.

Doing logic with Power Point, A Note about Notes…

Do not allow the ability to review these slides to replace active note-taking in class. I WILL say things in class that you WILL be responsible for on quizzes and exams.

Significant terms will often be in CAPS or BOLD type. Do NOT ignore them. Learn them.

What is Logic? Historical Answer -Logic is one of the main branches of

philosophy. It is the study of rational argument and inference.

Philosophical Answer –Logic is the study of arguments and

their properties. It is the methodological core of all intellectual disciplines.

About Arguments The main object of study in introductory

logic is the ARGUMENT. An argument in the logical sense is not a

disagreement. Rather, arguments are objects or structures in which certain claims are supposed to support one or more other claims.

We distinguish arguments primarily by looking at what sort of support they are meant to provide to the target claim.

Premises and Conclusions

In an argument, the claim that is supposed to be supported is called the ‘CONCLUSION’

The claims which are meant to support the conclusion are called ‘PREMISES’

All Arguments can be expressed as a set of specific premises with a conclusion.

Standard Form of an Argument

An Argument is said to be in STANDARD FORM when the premises are presented in a list followed by the conclusion.

This means that the first two things you must be able to do are 1) Identify and Distinguish individual claims (Propositions) and 2) Determine which claim is the conclusion.

An Example of Standard Form

[S] Socrates is mortal because all men are mortal

Standard form isolates conclusion and lists ALL premises.

1) All men are mortal (given premise)2) Socrates is a man (implied premise)3) Socrates is mortal. (Conclusion)

‘because’ is a ‘premise indicator’

LOGIC is a kind of….MIND CONTROL…

1) If Tom is tall then Frank is from Ohio.2) Tom is tall.

…3) Frank is from Ohio

The conclusion is unavoidable…it is as if the argument puts the conclusion in your mind.

OVERALL PLAN: Move from Simple to Complex

We will start be considering the nature of propositions themselves, not as parts of an argument.

We will then consider the roles propositions play in arguments and the possible types of relationships that might hold between premises and conclusions.

Propositions

When we spoke loosely of ‘claims’ we were speaking of what philosophers call: “Propositions.”

A proposition is a unit of cognitive information.

A proposition is either true or false. The same proposition can be

expressed in many ways.

Sometimes, there are fireworks in Logic!

Propositions and Information

A unit of information is the sort of thing that can be expressed with a declarative sentence.

A SIMPLE PROPOSITION is a unit of information, which has no parts that are propositions.

A COMPLEX PROPOSITION is a unit of information what has at least one proposition as a proper part.

Examples of Statements and Propositions

1)The cat is in the garage.

2a) The 43rd President lives in the White House.

2b) George W. Bush lives in the White House.

3a) Tom is tall and so is Fred.3b) Tom is Tall. Fred is Tall.

Conditional Propositions (1)

• Some Complex Propositions express a relation between a condition and a logical consequence of that condition.

• These are called CONDITIONAL PROPOSITIONS.

• They are usually expressed in the form:

IF X, then Y

Conditional Propositions (2) [*] If Tom is Tall, then George is in

Chicago.

The Condition in * (Tom is Tall) is called the ANTECEDENT.

The Logical Consequence in * of the condition being satisfied (George is in Chicago) is called the CONSEQUENT.

Truth and Propositions I

Every Proposition is either True or False.

This is the TRUTH VALUE of a proposition.

There are many philosophical theories about truth. [We will (mostly) assume that we have the ability to determine is a proposition is true or false.]

Truth and Propositions II

Logic is NOT concerned simply with WHETHER A PROPOSITION IS TRUE.

Logic is concerned with what we could infer from a proposition, if that proposition were true.

INFERENCE

Inference is the cognitive transition from evidence or reasons to some belief that is supported by the evidence or reasons in question.

There are two main kinds of inference: Deductive Inference and Inductive Inference.

Logic can also CALM your mind…