Logic

Question

How to approach the question where , 2 premises are given and conclusion is asked, what i know is that i can check whether it will be a valid. ?

there will be flood.

if it is raining for long , there will be flood .

what will be conclusion of both the premises. ??

Comments

i dont think qs is correctly framed...just check modus tollence and modus ponens

Answer 1

You can not conclude here anything . This is fallacy of affirming the conclusion.

there will be flood. -> Lets say we write it as F

if it is raining for long -> R

if it is raining for long , there will be flood .-> R->F

Now we have

F

R->F

We can not conlude anything here. As we are affirming conclusion here, but it does not derive anything.

So we can say from above Two statements, " there will be flood." Same statement given to else, Nothing more.

 

More Info->

See you have statement p->q

Then if you say q is true.

p->q,q => This is fallacy of affirming the conclusion.You can not derive here.

Also this is called fallacy of converse. i.e. If you derive p, then it is because you are assuming q-> p, which is incorrect.

Second one ->

p->q,~p => Fallacy of denying the hypothesis, You can not derive anything here..

If you try to derive ~q, then you are saying that ~p->~q, which is incorrect. It is also called fallacy of inverse.

Comments

and ya this is the answer. still i want to know when to use $\ni$ fallcy and when to use " fallcy for confirming the consequences"

Answer 2

(there will be flood ) AND (it is not raining for long  OR there will be  flood )

 

===>> there will be flood.

Comments

You are getting into fallacy of affirming the conclusion. Remember that (p->q) != (q->p)