Why you can't compare apples and oranges: False Analogy

False analogies are logical fallacies, and they occur when two things are incorrectly compared so as to draw a false conclusion. No two scenarios or ideas are exactly the same, nor do they so different that there is nothing similar about them. Therefore, no analogy is perfect, so we have to take care to avoid focusing on superficial similarities while ignoring fundamental dissimilarities. This is a very common fallacy because our language functions partly through comparisons; we use them to teach and to explain situations; we use comparisons in deciding how to handle new experiences; and we use them to make unfamiliar situations and ideas more familiar, thus helping us avoid acting out of fear. However, it is unwise to rely on analogies in making arguments because they will undoubtedly fail in key aspects.

How it applies: This fallacy is very common in the anti-evolution and intelligent design community. For example, claiming that the probability of a complex organism evolving by chance is the same as a tornado ripping through a junkyard and creating a 747 by chance - a very common analogy – is false. Evolution doesn’t work by chance but through the accumulation of changes, so it fails on a fundamental level. The “watchmaker” analogy by William Paley is the founding idea behind the intelligent design movement and is also a false analogy. The analogy is that the universe is like a watch, watches have been created by an intelligent being (a “watchmaker”), and so the universe must also have been created by an intelligent being. However, there are too many dissimilarities between watches and the universe to make this a valid comparison (not only does a watch bear little resemblance to a universe, the universe, being everything we have ever experienced has nothing to which it can be adequately compared.)  Invoking a creator because "DNA is a code" is also a false analogy (contrary to codes, DNA precedes the information it helps create).

Examples:

• “Customers are always right, and as a student, I’m paying you to teach me, so I demand that I get an A.” (Students are not customers purchasing grades; they are paying for the opportunity to learn. It is their choice as to how well they learn.)
• “If we legalize gay marriage, next we'll legalize marriage between men and their pets.”
• “Iraq is another quagmire, just like Vietnam."
• “Feminazi.”
• “Meat is murder”
• “What's the big deal about the early pioneers killing a few Indians in order to settle the West? After all, you can't make an omelette without breaking a few eggs.”
• “Just like an alley cat needs to prowl, a normal human being can’t be tied down to one single lover.”
• “Employees are like nails. Just as nails must be hit in the head in order to make them work, so must employees.”
• Opponent of a bill that would ban the use of chlordane, found to cause cancer in lab animals, says, “This bill reminds me of legislation that ought to be introduced to outlaw automobiles” on the grounds that cars kill people, said Rep. Tom DeLay, R-Texas, who owns an exterminating business. (Associated Press, June 25th, 1987)
• “People who have to have a cup of coffee every morning before they can function have no less a problem than alcoholics who have to have their alcohol each day to sustain them.”
• “Making people register their own guns is like the Nazis making the Jews register with their government. This policy is crazy.”
• “If one were to listen to only one kind of music or eat only one kind of food, it would soon become tasteless or boring. Variety makes eating and listening exciting and enriching experiences. So it seems to me that an exclusive sexual relationship with only one partner for the rest of ones life, that is, marriage, does not hold out much hope for very much excitement or enrichment.”
• “Smoking cigarettes is just like ingesting arsenic into your system. Both have been shown to be causally related to death. So if you wouldn't want to take a spoonful of arsenic, I would think that you wouldn't want to continue smoking.”
• “Because human bodies become less active as they grow older, and because they eventually die, it is reasonable to expect that political bodies will become less and less active the longer they are in existence, and that they too will eventually die.”
• “Tofu is like meat: both have the essential protein for building muscle mass.”
• “Tofu is like meat: just as we having regulations against inhumanely killing animals, we should have regulations against inhumanely harvesting soy beans.”