quick fallacy question: Philosophy Forums

Philosophy Forums » Introduction to Philosophy / Factual Issues / Books » quick fallacy question » quick fallacy question

quick fallacy question

quick fallacy question

kinna
Initiate

Usergroup: Members
Joined: Oct 27, 2009

Total Topics: 1
Total Posts: 1

Posted 10/27/09 - 09:51 PM: Subject: quick fallacy question	#1
Hi, first post and not avery exciting one, Is there an actual fallacy concerning the use of what you are trying to disprove as a premise in the argument? i.e. using common sense knowledge to disprove common sense? sorry if this seems like a dumb question. Thanks

Postmodern Beatnik
I Just Work Here

Usergroup: Administrators
Joined: Nov 18, 2005

Total Topics: 17
Total Posts: 2102

Posted 10/28/09 - 09:43 AM:	#2
kinna wrote: Is there an actual fallacy concerning the use of what you are trying to disprove as a premise in the argument? i.e. using common sense knowledge to disprove common sense? Generally not, though it depends on how you are using the premise. If you are trying to show how a given premise collapses in on itself by generating contradictions, there is no fallacy involved. In fact, you would be using a very common argument form: reductio ad absurdum. Such cases don't need the premise to be true for the argument to work as they are only demonstrating the unacceptable consequences of taking the premise seriously. This is by far the most common way of using something to disprove itself. If you need the premise to be true for your argument to work, however, you could land yourself in trouble. Let's say that you believe premises A, B, C, and D are true and that they disprove x. It could still be the case that your own justification for, say, premise C subtly relies on x in a way you didn't realize. So you can't believe C and ~x. This vitiates the original argument, but it may set you up with an argument of the first type. Because if x entails C, and if C combines with A, B, and D to give you ~x, then you are well on your way to a reductio argument. You'd still need to justify A, B, and D, of course, but that's true regardless (unless they can also be justified by x; then you have yourself a full-fledged reductio argument).
"The key to being a good manager is keeping the people who hate me away from those who are still undecided." --Casey Stengel

Hanover
The Highest Rank Possible

Usergroup: Members
Joined: Nov 30, 2008
Location: Atlanta

Total Topics: 8
Total Posts: 919

Posted 10/28/09 - 10:43 AM:	#3
kinna wrote: Hi, first post and not avery exciting one, Is there an actual fallacy concerning the use of what you are trying to disprove as a premise in the argument? i.e. using common sense knowledge to disprove common sense? sorry if this seems like a dumb question. Thanks In formal deductive logic, you can prove the validity of a conclusion by asserting its negation and then showing that the negation leads to a contradiction. Or to be more clear (but still likely unclear), if you have a set of premises and expect the result to be X, if you assert ~ X (not X) and then are led to the conclusion of X, then you can be certain that X is the case because X and ~ X cannot simultaneously exist. It's referred to as proof by contradiction. http://en.wikipedia.org/wiki/Proof_by_contradiction.
"Nothing is impossible for the man who will not listen to reason." John Belushi, "Animal House" "I have opinions of my own --strong opinions-- but I don't always agree with them." G.W. Bush

Postmodern Beatnik
I Just Work Here

Usergroup: Administrators
Joined: Nov 18, 2005

Total Topics: 17
Total Posts: 2102

Posted 10/29/09 - 06:09 AM:	#4
And just to confuse things further, proof by contradiction and reduction ad absurdum are two names for the same argument form. Luckily, Hanover was thoughtful enough to post a link for you.
"The key to being a good manager is keeping the people who hate me away from those who are still undecided." --Casey Stengel

Mako
Assistant Professor

Usergroup: Members
Joined: Feb 15, 2006
Location: In transit, somewhere in Nanjing

Total Topics: 14
Total Posts: 314

Posted 10/29/09 - 07:30 AM:	#5
Sounds like it's a case of 'begging the question' (petitio principii) except it's attempting ot 'disprove' rather than prove. Either way, it's a 'fallacy of presumption.'
"To alcohol. The cause of, and solution to, all of life's problems." ~ Homer Simpson

Postmodern Beatnik
I Just Work Here

Usergroup: Administrators
Joined: Nov 18, 2005

Total Topics: 17
Total Posts: 2102

Posted 10/31/09 - 08:28 AM:	#6
Mako wrote: Sounds like it's a case of 'begging the question' (petitio principii) except it's attempting to 'disprove' rather than prove. Either way, it's a 'fallacy of presumption.' Again, not necessarily. Reductio arguments always assume what they are trying to disprove, but there is nothing fallacious or invalid about reductio arguments per se.
"The key to being a good manager is keeping the people who hate me away from those who are still undecided." --Casey Stengel

Sorry, you don't have permission to post. Log in, or register if you haven't yet.