A Logical TheoryDr. Akhlas AhmedIBT, City Campus

Feb 4th, 2017Lecture # 3

A Logical Theory begins with the concept of an argument.

Collection of staements in the form of reasoning are called Arguments.

These staements are called premises, intended to support or infer a claim (conclusion).

Each staement has a truth value either true or false.

Conclusion necessarily/ certainly follow from premises called Deductive.

Conclusion necessarily/ certainly follow from premises called Deductive.

A deductive argument is any argument that aims to show that its conclusion must be true.

Its aim is to establish its conclusion. The implicit or explicit claim, in a deductive argument, is therefore that if the premises are true then the conclusion is completely certain to be true as well.

Conclusion follow from premises with some probability called Inductive.

An inductive argument aim is to show that its conclusion is probably true although not certainly true.

In inductive argument claims (in so many words) only that if the premises are true, then the conclusion is likely or reasonable (but not certain).   

Deductive indicators...When conclusion with wording such as! Therefore it must be that… It necessarily follows that… Therefore it is certain that… It is conclusively proven that…These phraes are called deductive indicators.

Inductive indicators...When conclusion with wording such as! Therefore it is probably the case that… It is likely that… Therefore it is reasonable to conclude that… These phraes are called inductive indicators.

A deductive argument that succeeds in showing that its conclusion must be true if its premises all are true is called a valid deductive argument. 

A deductive argument that fails to show that its conclusion must be true if its premises are true is called an invalid deductive argument.

Valid…example: 1. All human beings are mammals.2. All mammals are warm-blooded.3. Therefore it must be that all human beings are

warm-blooded.Invalid…example:1. All human beings are mammals.2. All dogs are mammals. 3. Therefore it must be that all human beings are

dogs..

1. All students are millionaires.2. All millionaires are Buddhists.3. Therefore, all students must be Buddhists.In this example argument, about students and Buddhists, was valid, but unsound

A sound argument has two characteristics:• All of its premises are true.• It is valid. .

1. All whales are mammals.2. All mammals are animals.3. Therefore, it must be that all whales are

animals. This example is both valid and sound:

Class Activity

“Love is a decision – not an emotion”

“Logic is the beginning of wisdom, not the end”

“Logic is the anatomy of thoughts”

“Logic is art of going wrong with confidence”

“Logic is the eye of logician”

“I was born intelligent -education ruined me.”

“Practice makes perfect.... But nobody's perfect..... .

so why practice?.”

“If it's true that we are here to help others,then what exactly are the others here for?

“Since light travels faster than sound,people appear bright until you hear them

speak.”

“How come "abbreviated" is such a long word? ”

“Money is not everything.There's MasterCard & Visa. ”

“If your father is a poor man,it is your fate but,

if your father-in-law is a poor man,it's your stupidity.”

“One should love animals.They are so tasty. ”

“Behind every successful man, there is a woman

And behind every unsuccessful man, there are two. ”

“Every man should marry.After all, happiness is not the only thing

in life.”

“The wise never marry.and when they marry they become

otherwise.”

“Success is a relative term.It brings so many relatives. ”

“Never put off the work till tomorrowwhat you can put off today.”

“"Your future depends on your dreams"So go to sleep”

“"There should be a better way to start a dayThan waking up every morning”

“Hard work never killed anybody"But why take the risk”

“Work fascinates me"I can look at it for hours”

“God made relatives;Thank God we can choose our friends.”

“The more you learn, the more you know,The more you know, the more you forgetThe more you forget, the less you know

So.. why learn.”

“A bus station is where a bus stops.

A train station is where a train stops.

On my desk, I have a work station.... what more can I say........”

Q/ A Session