A "Genetic Fallacy" is a line of "reasoning" in which a perceived defect in the origin of a claim or thing is taken to be evidence that discredits the claim or thing itself. It is also a line of reasoning in which the origin of a claim or thing is taken to be evidence for the claim or thing. This sort of "reasoning" has the following form:
The origin of a claim or thing is presented.
The claim is true(or false) or the thing is supported (or discredited).
It is clear that sort of "reasoning" is fallacious. For example: "Bill claims that 1+1=2. However, my parents brought me up to believe that 1+1=254, so Bill must be wrong."
It should be noted that there are some cases in which the origin of a claim is relevant to the truth or falsity of the claim. For example, a claim that comes from a reliable expert is likely to be true (provided it is in her area of expertise).
The Genetic Fallacy is a type of ad hominem that has the following form:
Person A presents an argument.
Person B attacks person A's character.
Therefore person A's argument is invalid.
The reason why an Ad Hominem (of any kind) is a fallacy is that the character, circumstances, or actions of a person do not (in most cases) have a bearing on the truth or falsity of the claim being made (or the quality of the argument being made).
- "The current Chancellor of Germany was in the Hitler Youth at age 3.
With that sort of background, his so called 'reform' plan must be a facist program."
- "I was brought up to believe in God, and my parents told me God exists,
so therefore He must."
- "Sure, the media claims that Senator Bedfellow was taking kickbacks.
But we all know about the media's credibility, don't we."
- Freud was a cocaine-snorting pervert: why listen to him?