Definition from the Merriam-Webster dictionary: Main Entry: analˇoˇgy Pronunciation: &-'na-l&-jE Function: noun 1 : inference that if two or more things agree with one another in some respects they will prob. agree in others 2 a : resemblance in some particulars between things otherwise unlike : SIMILARITY b : comparison based on such resemblance Did you notice that the two definitions contradict each other? Definition #1 is the inference that two situations which are similar in some respects will probably be similar in most respects, while definition #2 explicitly denies anything but a very narrow similarity! The English language can be a rather blunt instrument at times, can't it? So many words have more than one meaning, and "analogy" is no exception. So which definition applies to the kind of argumentative analogy you would use in a debate? Well, let's run through examples of our two definitions, shall we? Let's call the first definition a Type 1 Analogy, and the second definition a Type 2 Analogy: Type 1 example: "Wow, your child has Down's Syndrome? Well, having a child with Down's Syndrome is a lot like buying a new car and discovering that it's a lemon, isn't it? In both cases, you get something that costs a ton of money and is supposed to bring joy to your life, but it's got all kinds of problems. Take my new car for example; I've had to take it in for service three times in the last six months alone! So the two situations are mostly alike, and I definitely know how you feel." (please note: if you said this to a real person with a Down's Syndrome child, he might try to kill you). Type 2 example: "You don't understand how a bad liver causes so many different kinds of problems all over different areas of your body? OK, the liver filters blood, right? So think of the liver as the oil filter in your car. If it's clogged up, everything will eventually start going south." Example #1 serves no real point other than to claim that the two situations are similar, ie- its only point is to state itself, rather than serving some other point, as most argumentative analogies do. The second one, on the other hand, is a classic example of an argumentative analogy, of the kind that you will often hear during a debate. Your body and an automobile are grossly dissimilar in most respects, but they are similar enough in this one aspect that you can illustrate something about the body by using the simplified analogy with the automobile. Simple enough, no? Ah, but there's the rub: because you have two different kinds of analogies, people will often employ a rebuttal which would be valid against one type of analogy, but not valid against another. You can defeat a Type 1 analogy by pointing out the myriad ways in which the two situations are different, because the whole point of the analogy is to claim that the two situations are mostly alike. But it would be absurd to do that with a Type 2 analogy; of course cars and human bodies are different, but the point is that they are similar in the one aspect under discussion, so dissimilarities in other areas are irrelevant. Deceptive attacks upon analogies Analogies are one of the most useful rhetorical tools to any debater, but they are often attacked by people without justification. Let's look at an example: ADAM: How can you say that you don't have to pay back your student loan because you don't agree with capitalism? This is like losing a game of poker, and then declaring that you don't have to pay up because you don't agree with gambling! Once you choose to enter the game, you agree to abide by its rules. KARL: No, that's different. Poker is a harmless card game between individual members of the proletariat, not a part of the exploitative system of bourgeoisie property that dehumanizes mankind and devalues the human concepts of work, family, and community. Your analogy is completely false and clearly influenced by capitalist indoctrination. You will most likely shake your head at the above exchange; Karl is obviously wrong in dismissing the analogy on such grounds, but can you explain precisely why he's wrong? That's the trick, and that's what you should be able to do if you understand analogies. So what makes Karl wrong? Simply put, this is clearly an example of a Type 2 analogy, and Karl has responded by treating it as a Type 1 analogy. It's a rhetorical shell game which can easily confuse an inexperienced or inattentive debater, and it's one of the oldest anti-analogy tricks in the book. How do we know it's a Type 2 analogy? Well, for starters the subject is obviously not the level of similarity between banking and poker, but rather, it's about the ethics of paying back loans. This analogy is obviously designed to make a point about the consequences of voluntarily entering into agreements with known rules: something which is similar about bank loans and poker games. Adam even made a point of repeating this point of similarity for clarity (a good idea when using analogies). Therefore, it's fairly obvious that we're talking about a Type 2 analogy, so Karl's response is irrelevant, and perhaps even deliberately dishonest. The question now becomes: how should Adam defend his analogy? His first impulse might be to simply challenge Karl to put his ideas to the test, ignore the rules of capitalism, and wait to see what happens when those rules fail to ignore him in return. But that's an emotional response, not a logical one. His second impulse might be to argue that poker games and banking systems are not really that dissimilar, which would only play into Karl's hands because they really are quite dissimilar in most respects, and Adam would only end up painting himself into a corner by defending a weak position. Worse yet, he would have allowed Karl to quietly change the subject, from the ethics of refusing to obey agreed-upon rules to the level of similarity between poker and banking. If he makes this mistake, then it will eventually appear to bystanders that he is losing the argument, even though his initial position was strong. There are few things more annoying in a debate than to start with a strong position and end up being drawn into a debate that revolves around the methods you used in order to support that position. So once again, how should Adam defend his analogy? There are two things to keep in mind at this point: The analogy is a means to an end. It is not an end in itself, so it is only important to defend the point that was being made by the analogy, not the analogy itself. In this case, he should remind Karl that regardless of other differences, poker and a bank loan are similar in the sense that you voluntarily enter into an agreement with rules that are known to you at the time. He should not let Karl trick him into debating the strength of the analogy; he can freely admit that it's weak in every aspect other than the one under discussion, which is all that matters. When you're not sure how to respond to a deceptive technique by your opponent, a reliable default technique is to simply point out what he's doing. In this case, Adam could explain to the audience that Karl is pretending the analogy was intended to show that banking and poker are similar in every respect even though it was obviously meant only to address Karl's particular argument, which Karl has failed to defend. If Adam is quick on the draw, he might also point out that it's a strawman distortion on Karl's part to pretend that the analogy was ever intended to describe any similarity other than the one Adam pointed out. Valid attacks upon analogies Of course, not all attacks on analogies are deceptive. There are plenty of analogies which really are false, and they tend to fall into three categories: Strawman distortions of your position. This technique distorts your position and then produces a situation which is analogous to the distorted version rather than your real position. You could call it a false analogy or a strawman distortion; either accusation would be valid. A common example is the "million monkeys typing on a million typewriters to write Shakespeare" creationist analogy for natural selection. This analogy assumes that natural selection is random when it is not. In fact, the whole point of natural selection was to come up with a mechanism for directing the process of evolution. Inaccurate description of the point of comparison. This usually occurs through simple ignorance, particularly in science-related debates where one or both of the participants often has no idea how the science actually works. A good example is the "blind watchmaker" analogy in creationism, where creationists who apparently flunked high-school chemistry assume that a pile of watch parts and a pile of amino acids are analogous in terms of the unlikelihood of spontaneous assembly (even though a superficial knowledge of basic chemistry would tell us why organic compounds can and do spontaneously react to form structures, while metal gears do not). Circular logic, ie- analogies which attempt to support a premise by assuming that same premise. For example, "How can you reject salvation in Christ? If someone offered you the keys to a magnificant mansion and asked you only to thank him, wouldn't you do it?" Notice how there's really no logical argument here; just the assumption that this "salvation" scheme works, and an analogy which incorporates that same assumption in order to justify it: a clear case of circular logic. Frankly, any use of analogies to support a premise rather than a point of logic should be looked at suspiciously. Analogies are normally used to justify logical connections, not premises. Conclusion The analogy is one of the most popular rhetorical instruments of debate. But unfortunately, misuse, abuse, and unfair dismissal of analogies is so common and so easy (particularly in contentious political or religious debates) that they often lose much of their utility. Remember the rules for how to properly use and refute analogies, remind others of those rules when necessary, and be careful. After all, the line between logical debate and alpha-male jockeying for supremacy can sometimes be thinner than you think.