## INTRODUCTION TO LOGIC

introduction to logic

__NATURE OF LOGIC____Origin of logic__

Logic started at around the fourth century. Aristotle is known as the father of logic. He derived the word logic from the Greek word **“LOGOS” **which means** “discourse”. **To Aristotle, logic is considered as an **“organon” (**an instrument which allows one to attain the truth in discourse in the course of thinking. Logicians like **John Venn, George Boole, and Godfrey Leibniz **also contributed in the development of logic.

__Formal definition of logic __

Logic is the branch of philosophy which deals with the methods and principles used to distinguish correct reasoning from incorrect reasoning.

__Logical concepts__

**Proposition:**it is a statement which can either be true or false.**Truth value:**it refers to whether a proposition is true or false.**Argument:**an argument is a group of propositions in which one of them called the conclusion is derived from the others called the premises. E.g.

All girls are beautiful

Shekinah is a girl

Therefore Shekinah is beautiful

**Truth and validity:**truth and falsity deals with propositions while validity deals with arguments**A valid argument:**This argument whose conclusion follows from the premises and is perfectly related to the premises e.g.**An invalid argument:**this is an argument whose conclusion does not follow from the premises**Sound argument:**this is an argument whose is valid and all its premises are true.**Unsound argument:**this is an invalid argument with true premises or a valid argument having at least one of the premises false**Strong argument:**this is an argument in which the premises provide partial support for the conclusion.**Weak argument:**this is an argument that is not probable. That is if its premises are true then the conclusion is also true.**Cogent argument:**this refers to an argument that is both strong and has only true premises.**Uncogent argument:**this is an argument that is either weak or strong with at least one false premise

__The purpose of logic__

- Logic drills the mind to draw right conclusion and avoid wrong ones
- Logic helps one to acquire and retain knowledge which can permits one to investigate and detect bad arguments.