1. GST 113: LOGIC, PHILOSOPHY AND HUMAN EXISTECE
WHAT IS LOGIC?

2. LESSON OBJECTIVES For this class our focus shall be on four things
1. To introduce the student to what logic is
2. Trace a brief history of logic as a branch of philosophy
3. Discuss the importance of logic to philosophy, other academic disciplines, and to life generally.
4. Discuss the Three Laws of Thought.

3. ETYMOLOGY OF THE WORD LOGIC
Etymology has to do with tracing the origin of a word. Etymology deals with tracing the historical development of a word.
Logic is from the Greek word- logike
Logic is from the Latin word- logica
From the etymological definition logic refers to the art of reasoning

4. Logic as a BRANCH of Philosophy
Although there are many ways in which one can use the word, logic, we are concerned, in this course, with the employment of logic in the technical sense
In the technical sense, logic is a branch of philosophy
As a branch of philosophy it is dedicated to the study of correct reasoning
It is the study of valid inference

5. What a training in Logic equips one with
A training in logic equips one with skill for evaluating arguments
One is able to separate good arguments from bad arguments; separate valid arguments from invalid arguments, deductive arguments from inductive arguments; and sound arguments from unsound arguments.
One is able to detect faults in reasoning/arguments

6. TWO IMPORTANT THINGS ONE IS ABLE TO DO BETTER WITH THE STUDY OF LOGIC
There is no doubt that people who have never studied logic are able to do some things that those who have studied logic do. However, a training in logic equips one with the necessary skill and better enhances the ability to do better certain things with greater accuracy.
There are mainly two things one is able to do well with the study of logic
1. the evaluation of the arguments of others
2. the construction of good arguments of one’s own ( a good argument will be one without flaws i.e. a argument without fallacies)

7. OBJECT OF STUDY OF LOGIC
The object of study in logic is ARGUMENT
What we do in logic is to analyse arguments
The analysis of arguments essentially has to do with the SEPARATION OF GOOD ARGUMENTS FROM BAD ARGUMENTS

8. What the ANALYSIS of arguments entails
When we analyse arguments, one may be doing one of the following
1. Separating an argument from other pieces of writing e.g., explanations, questions, narration, etc.
2. identifying the type of argument one is encountering
3. separating an argument into premises and conclusion
4. identify whether a fallacy has been committed in an argument or not

9. Brief History of Logic
The first philosopher that started off logic is ARISTOTLE. It was he that developed systematically and codified the criteria for analysing and evaluating arguments.
Aristotle’s principal contributions are in the areas of
syllogistic logic
modal logic
the classification of some informal fallacies.

10. Other contributors to logic
Others who have made significant contribution in one way or the other include:
Chrysippus, Peter Abelard, Gottfried Wilhelm Leibniz, Bernard Bolzano, Augustus De Morgan, George Boole, William Stanley Jevons, John Venn, Charles Sanders Peirce, Emile Post, Ludwig Wittgenstein, Bertrand Russell

11. IMPORTANCE OF LOGIC (TO THE PHILOSOPHER)
Philosophy is an academic discipline in which the evaluation and advancement of arguments are important tasks for philosophers.
1. The study of logic helps philosophers to put up good arguments
2. The study of logic enables the philosopher to be able to evaluate other peoples’ arguments and pinpoint holes in them

12. IMPORTANCE OF LOGIC TO OTHER DISCIPLINES
Logic is of great importance to disciplines like Law, Intelligence and Security Studies, Computer Science, and Mathematics
The first way in which logic is of importance to other academic discipline is that all academic discipline deals with evaluation of arguments of others. As such competence in logic sharpens the acumen of professionals in engaging other people’s ideas.
Lawyers need to be able to evaluate the argument of other lawyers in court and pick loopholes
In Intelligence and security studies, one needs to be trained in a way that one will have to be able to see through the positions of suspects

13. THE IMPORTANCE OF LOGIC TO LIFE GENERALLY
We encounter arguments everyday in dealing with friends, politicians, business organisations. Logic enables one to be able to separate psychologically persuasive arguments from rational arguments based on facts.
A training in logic is able to ensure the development of a MORE CRITICAL MIND in the analysis of events and arguments encountered on daily basis. One then begins to question things read, watched, and listened to as one begins to separate psychologically persuasive points of views from arguments with merits.

14. There are three laws of thought. They are: 1. The Law of Identity
THE LAWS OF THOUGHT
There are three laws of thought. They are:
1. The Law of Identity
2. The Law of (Non)contradiction
3. The Excluded Middle

15. The Law of Identity (P ⊃ P)
This law holds that if any statement is true then it is true.
EXAMPLE “it is raining.” The Law of Identity stipulates that this statement is identical to itself such that the truth of the statement is not altered if one says “it is raining then it is raining.”
Logical form is P ⊃ P

16. The Law of (Non)Contradiction
This law holds that “No statement can be both true and false at the time.”
Take for example the statement “it is raining.” If in actual fact this statement is true then one would be contradicting oneself if one holds, at the same time, that “it is not raining” is a true statement as well.
Thus, one must not contradict oneself by affirming a proposition and denying the same proposition at the same time. Thus, this law is saying “every statement of the form ‘P.~P’ is self-contradictory.”

17. The Law of Excluded Middle
This law asserts that “any statement is either true or false.” There is no middle ground.
The statement: “it is raining” is either true or false. It is true if in actual fact it is raining. It is false if, when the claim is made, it is actually not raining. There is no third option
The logical form is ‘PvP’