Shifting the Burden of Proof – occurs when speakers do not prove their own claims while forcing others to prove them.
 

A standard rule in argumentation is “he who asserts must prove,” meaning that the writer bears full responsibility to prove that his or her claims are true.  Writers and speakers, especially when cornered with tough questions, often speak authoritatively, but they sometimes assume that their assertions are valid and place the onus of proof onto the audience.
 

FOR  YOUR  INFORMATION    

If someone claims to know a fact, always look at its source.  If the arguer cannot validate or justify his own remarks, then they probably are not valid (and cannot be considered valid anyway until proven otherwise).  The audience does not bear any responsibility to prove the speaker’s arguments.
 

This fallacy is also called an “appeal to ignorance” because the action of passing this responsibility onto the audience suggests that a group of unprepared non-experts is appearing qualified to speak, when they clearly are not.
 

EXAMPLE 1

A bitter dropout spouts: “College students spend four years of their lives and thousands of their parents' dollars trying to get as little as possible out of their college education, provided only that they get their coveted diplomas.”

This writer makes an overgeneralization by claiming that all college students are lazy parasites.  Yet, this writer offers no evidence to support the assertion, making his argument worse through his use of distortion, loaded language, and poisoning the well.  The audience does not bear the responsibility of proving these points – the author does, since he made the claim.

Also, the audience should never agree with the author’s assumptions, even if they seem reasonable or believable.  The old phrase “never assume” still applies here.  A safe attitude says “Prove it, or don’t bother arguing the point.”

 
EXAMPLE 2

A true skeptic says: “Aliens don’t exist because no one has ever proven that they do.”

The author makes an unsubstantiated claim here as well.  True, without an alien body or a close encounter, people should feel skeptical about life on other planets.  This speaker mistakingly assumes that his audience will agree with him, even though the only “evidence” he provides is the lack of evidence.  Until he discovers some proof, his claim must remain invalid.  He may be right, but we cannot agree that he is correct based on his own misunderstanding.  What we don’t know cannot be used as evidence for (or against) anything.
 

Hundreds of years ago, scientists made the same claim against bacteria – “I don’t see it, so it must not exist.”   After the microscope allowed us to see smaller objects, the existence of bacteria was finally proved.   These early skeptics fell into the trap of appealing to their own ignorance – another type of fallacy.