Genetic – assuming that the origin of something nullifies its value today.
 

A person commits the genetic fallacy when he argues against some claim by pointing out that its origin (genesis) is tainted (or that it was invented by someone who deserves our contempt).  Thus, one might attack the Declaration of Independence because Thomas Jefferson was a slave owner, yet he wrote that “all men are created equal.”  Although this uncovers some hypocrisy in Jefferson’s character, his moral faults by themselves do not nullify his idealistic vision of America.
 

EXAMPLE

A proud progressive speaks: “Capital punishment arose in barbarous times; but we claim to be civilized; therefore, we should discard this terrible relic of our past.”

This argument should not be convincing because the question of the death penalty in our society must be decided by the degree to which it serves our purposes.  This makes a law’s historical origins irrelevant to the issue of whether or not these laws serve our needs today.  Certainly, we have eliminated torture from our criminal justice system because we have found more humane ways of collecting evidence and discovering the truth behind crimes.  We have simply found a more streamlined use of the death penalty, so we cannot compare capital punishment today to the torturous inquisitions of the past.

True, many executioners throughout history must have been merciless and brutal, even toward the innocent.  We commit the genetic fallacy when we continue to apply these assumptions, perspectives, and emotions from the past to today’s world.  Again, examine the context.  We can reject the death penalty on moral or ethical grounds, but not on the origins of the word or deed.