Analytical Thought 3 AIMS:

To identify reasons and conclusions

To define DEDUCTIVE logic

To examine 4 types of deductive logic

Explore LOGICAL FALLACIES Recap:

Deductive argument (logic) is an argument where it is impossible for the conclusion to be false if the premises are true.

for example:

All human beings are mortal.

Socrates is a human being.

Therefore, Socrates is mortal We will look at 4 types of deductive arguments:

Modus Ponens

Modus Tollens

Hypothetical Syllogism

Disjunctive Syllogism

Modus Ponens

If today is Tuesday, then I will go to work.

Today is Tuesday.

Therefore, I will go to work ... which can be expressed as:

If t then w

t

Therefore w Modus Tollens

This takes the form:

If f then o

Not-o

Therefore not-f If there is fire here, then there is oxygen here.

There is no oxygen here.

Therefore, there is no fire here Hypothetical Syllogism:

If s then r

If r then q

Therefore , if s then q

for example

If you study other cultures, then you realise the variety of human customs.

If you realise the variety of human customs, then you question your own customs.

Therefore if you study other cultures, then you question your own customs.

Disjunctive Syllogism:

This can be written as:

c or s

Not-c

Therefore s for example ...

Either I will choose cake or I will choose salad.

I will not choose cake.

Therefore, I will choose salad. Careful! OR can mean 2 things in English “p or q” can mean at least one of p or q is true (and possibly both).

This is the ‘inclusive’ definition and is used in logic.

“p or q” can also be ‘exclusive’

i.e. either p is true or q is true but not both Look at the 4 arguments and decide what type of deductive argument it is .... Example 1 ...

If he’s watching tv, he’ll fail his exams.

If he fails his exams, he will leave the university.

Therefore, if he’s watching tv, he will leave the university

Example 2 ...

Either he is watching tv, or he is revising.

He is not watching tv.

Therefore, he is revising

Example 3 ...

If he’s watching tv, he’ll fail his exams

He’s watching tv.

Therefore, he’ll fail his exams

Example 4 ...

If he’s watching tv, he’ll fail his exams.

He hasn’t failed his exams.

Therefore he wasn’t watching tv.

Logical Fallacies...

What are they? ... Fallacies are MISLEADING arguments ... Fallacies violate one or more of the rules for good arguments.

Fallacies are very common in everyday life and even academic life.

3 easy examples ... #1

He cannot accuse me of cheating because he has cheated WHY???? ...

defending an error in your reasoning by pointing out that your opponent has made the same error

This type of fallacy is called ...

Tu quoque #2

Only an untrustworthy person would run for office.

The fact that politicians are untrustworthy is proof of this because ...

the truth of the conclusion is assumed by the premises (the proposition is used to prove itself

This type of fallacy is called:

petitio principii

(Begging the Question) #3

John says that we should stay at home this evening. I disagree entirely. I can't understand why he never lets us have a good time because ...

misrepresenting an opponent's position

Straw man argument The blog ...

this is where you can find information about the module, links, and exercises to do ...

The address is ... ...

http://alex-analytical-2011.blogspot.com/ ...

Argument: "No Scotsman puts sugar on his porridge."

Reply: "But my friend Angus likes sugar with his porridge."

Rebuttal: "Ah yes, but no true Scotsman puts sugar on his porridge." paradox ....

A man says that he is lying; is what he says true or false?

Sorry :-( You have a midterm exam no need to panic....

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# analytical thought 3

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