Philosophers and logicians often refer to the genetic fallacy. It occurs when one attempts to rebut a belief, claim, or theory by only appealing to its source.
But casting asperions on the source does not mean that you have rebutted the truth of the claim. A lunatic on the street may walk around screaming that 2+2=4. Graffiti in the inner city might proclaim that E=MC2. Despite the less-than-reliable sources, both of the propositions are true.
Simple, right? Well many people employ this fallacy in the public square, and knowing it is essential for clearing the fog--especially in this year's political debate. Consider, for example, the Swift Boat Veterans for Truth and their claims. The Kerry campaign, to my knowledge, refuses to deal with their arguments and claims. Instead, their entire rebuttal consists of attacking the source--or even worse, the financial backers of the source. The arguments, however, remain untouched.
One doesn't need to take a class in logic or to read a textbook on logic in order to uncover logical fallacies. Aristotle didn't invent logic. He just used common sense to clarify and explain what we already know. If you are interested in a good logic textbook, I'd highly recommend Peter Kreeft's Socratic Logic. There's also a fine book written for kids on the subject: The Fallacy Detective.
