writing to convince

8/6/2019 Writing to Convince

1/13

CRITICAL THINKING & WRITING


2/13

WHAT IS AN ARGUMENT?

An argument (a piece of reasoning) is a set of

statements, one of which (the conclusion) is

maintained to be true on the strength of the

others (the premises).


3/13

WHAT IS AN ARGUMENT?

Argument = premises + conclusion

Every argument has exactly one conclusion and

at least one premise


4/13


5/13

RECOGNIZING PARTS OF

ARGUMENTS

Phrases that indicate a conclusion

Therefore

So

Thus

it follows that

as such


6/13

RECOGNIZING PARTS OF AN

ARGUMENT

Phrases that indicate a premise

Since

Because

As

For

due to the fact that


7/13

ENTHYMEMES

An enthymeme is an argument, one of whose

premises (or perhaps even the conclusion) is

implicitly suppressed, though intended as

present

Example:

John will die one day, because he is a man.

Whats the missing premise?


8/13

DEDUCTION VS. INDUCTION

An argument is said to be deductive in the casethat the conclusion is meant (by the arguer) tobe guaranteed by the premises (whether the

premises are true or not is a different matter). An argument is said to be inductive in the case

that the conclusion is meant (by the arguer) tobe made probable by the premises (whetherthe premises are true or not is a differentmatter).


9/13

EXAMPLES OF DEDUCTIVE

ARGUMENTS

Either John or Peter broke the glass. John did

not do it. So Peter did it.

John is taller thanP

eter.P

eter is taller than hisfather. So John is taller than Peters father.

Either John ofPeter is the King of Singapore.

John is not. So Peter must be the King of

Singapore.


10/13

EXAMPLES OF INDUCTIVE

ARGUMENTS

It has been raining for five days in a row. There

are dark clouds now. I conclude that it will rain

again today.

There are one million tickets in the lottery.

There is only one prize. I only have one ticket. I

conclude that I wont win the prize.


11/13

VALIDITY AND STRENGTH

If the conclusion of a deductive argument isindeed guaranteed by the premises, then theargument is said to be deductively valid.

Otherwise, it is deductively invalid.

If the conclusion of an inductive argument is

indeed made probable by the premises, thenthe argument is said to be inductively strong.Otherwise, it is inductively weak.


12/13

ARE THESE DEDUCTIVE ARGUMENTS VALID OR

INVALID?

If it rains, itll flood. If it floods, well drown. So ifrains, well drown.

You wont win unless you try. You wont try unless

you dream. So you wont win unless you dream. Either John or Peter will be here. Either Peter or

Mary will be here. So either John or Peter will behere.

No horses are found in Country A. Country A is

found to the north of Country B. So no horses arefound in the north of Country B.


13/13

ARE THESE INDUCTIVE ARGUMENTS STRONG OR

WEAK?

Every century in the past century has been

witness to at least one major war. So at least

one major war will be fought this century.

Youre wearing a red shirt today. So youll be

attacked by a bull.

writing to convince

Documents