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False and Imperfect Analogies

In an analogy, two objects or events, A and B, are supposed to be similar. Then, it is argued that since A has property P, B must also have property P. An analogy is false when A and B are materially different such that B doesn’t possess property P. 2) An imperfect analogy may succeed in predicting property P in B, but in B the property is possessed differently or only partially. So, analogies fail either by seeing an analogy where none exists, or by overestimating the value or significance of the analogy. However, determining whether an analogy is good, false, or imperfect is as much an art as a science. Accordingly, the examples provided below are not necessarily false or imperfect analogies. We leave that judgment to you. Furthermore, even a good analogy is not a proof and at most provides probabilistic or inductive evidence.

Examples
  1. "'A good marriage is like a game of baseball. In baseball, if a player follows the rules, the game will be a success. Likewise, in marriage, if the players stick to the rules the partners accept, the marriage will flourish.' ... Marriage and baseball may have a few surface similarities, but marriage is much more complex than baseball. The relationship between 'the rules' and 'success' is infinitely more intricate in marriage than it is in baseball." (Rozakis, The Complete Idiot's Guide to Public Speaking, p. 96.)
  2. Just as a map is a guide, not a literal copy, of the terrain to which it refers, the mind's eye is like an imperfect map of the external world. Though what we see may have some resemblance to the world itself, we do not see the world itself.
  3. A common prolife argument draws this analogy. A hunter who sees movement in the brush is not permitted to fire at will. Rather, he is expected to positively identify his target as a deer or foul, and not another hunter or hiker. When human life is at stake, we must err on the side of caution. Likewise, even if we cannot determine with certainty that a fetus is a human person, we should err on the side of caution and never abort.
  4. "England, France, and Germany are the great powers of Europe. Both England and Germany have signified their willingness to sign this treaty. We are therefore certain that the great powers of Europe will become parties to this treaty provided we give them the opportunity." (Ketcham, The Theory and Practice of Argumentation and Debate, p. 257.)
  5. "Gentlemen, suppose that all the property you were worth was in gold and you put it in the hands of Blondin, the famous rope-walker, to carry it across the Niagara Falls on a tight rope. Would you shake the rope while he was passing over it, or keep shouting to him, 'Blondin, stoop a little more. Go a little faster.' No. I am sure you would not. You would hold your breath as well as your tongue, and keep your hand off until he was safely over. Now, the government is in the same situation. It is carrying an immense weight across a stormy ocean. Untold treasure are in its hands. It is doing the best it can. Don't badger it. Just keep still and it will get you safely over." (U. of Wisconsin, The Principles of Effective Debating, p. 31.) » Abraham Lincoln employed this argument to quell the restlessness of some who were pressing him to act more forcefully during the Civil War. The analogy here is compelling, but the poles in the comparison are of such a disparate nature, it's difficult to appraise its force, not to mention that any argument intended to silence dissent is deserving of particular scrutiny.
  6. "For example, we might enumerate many points of external resemblance between the Whale and the Shark, and found upon them an analogical argument to the effect that the respiration-processes in the two animals must be similar. The whale, we might say, resembles the shark not only in all the common characters of Vertebrates, but also in its submarine habitat and in being (as regards many species) one of the very largest of marine animals. Like the shark, it is fish-like in external form, its fusiform body being well fitted for cleaving the water. Anteriorly its body passes into the head without any distinct neck, and posteriorly it is furnished with a swimming-tail into which the body gradually tapers. It has no hairy covering. Like the shark, again, it has a wide mouth, and it is of predaceous habit, feeding only on living animal nutriment. Therefore we may with great probability conclude that its method of respiration is like that of the shark — i.e., that it breathes the oxygen dissolved in the water, and has no need to be supplied with atmospheric air. But this argument is unsound. The points that we ought to have observed are the characters connected with the function of respiration. The presence of gill-slits in the shark and their absence in the whale is a difference so essential to the inquiry that its observation would at once have been sufficient to make our analogy fall to the ground." (Gibson & Klein, The Problem of Logic, pp. 359-60.)
  7. "Other people resemble me in many important respects: we are all members of the same species, and consequently we have quite similar bodies; we also behave quite similarly. When I'm in extreme pain I scream, and so do most members of the human species when they are in situation in which I would expect them to be experiencing pain. The argument from analogy claims that the similarities in body and behaviour between my own case and those of other people are enough for me to infer that other people are genuinely conscious in the way that I am. (Warburton, Philosophy, p. 145.)
  8. "But suppose I had found a watch upon the ground, and it should be inquired how the watch happened to be in that place; I should hardly think of the answer which I had before given, — that, for any thing I knew, the watch might have always been there. Yet why should not this answer serve for the watch as well as for the stone? ... For this reason, and for no other, viz. that, when we come to inspect the watch, we perceive ... that its several parts are framed and put together for a purpose, e. g. that they are so formed and adjusted as to produce motion, and that motion so regulated as to point out the hour of the day. ... [E]very indication of contrivance, every manifestation of design, which existed in the watch, exists in the works of nature; with the difference, on the side of nature, of being greater and more, and that in a degree which exceeds all computation. ... Were there no example in the world ... except that of the eye, it would be alone sufficient to support the conclusion which we draw from it, as to the necessity of an intelligent Creator. (Paley, Natural Theology.) » Basically, Paley argued that just as we infer from the complexity and purposefulness of a watch that there is a watchmaker, so too can we infer from these properties in the natural world that a Creator exists. To what extent the analogy has merit is the subject of considerable philosophical debate.
Critique
"[T]he weakness of such an argument can be exposed by proving: 1) That the details of comparison or contrast are not essential to the question at issue. 2) That the points of likeness (or difference) which are relied upon for the analogy are outweighed by the points of difference (or likeness) which are ignored. 3) That the conclusion reached by the argument from analogy is discredited by other kinds of argument. 4) That the facts known to be true of the analogous case are less likely to be true of the case in question. 5) That the alleged facts on which the analogy is based are not true." (Foster, Argumentation and Debating, 1908, p. 147.)
Comment
On the subjective art of appraising anologies...
"Because all analogies are, at some level, false (to use one of Ronald Reagan's examples, cutting the federal budget is not the same thing as a person going on a diet), this often is a very slippery type of fallacy. The force of analogy, like the force of metaphor, arises from its ability to help us look at some thing in a new way. ... [I]n certain circumstances, an analogy might go to far, it might impede our ability to think about and decide among various courses of action. Did Reagan's analogy between cutting the budget and going on a diet go too far? One probably could make a good argument that it did — that the analogy distorted the complex factors involved in cutting the budget. But the question of whether a particular analogy goes too far is, like beauty, in the eye of the beholder." (Jasinski, Sourcebook on Rhetoric, pp. 242-3.)
On the inconclusiveness of all arguments from analogy...
"Arguments from analogy, of course, are never conclusive. That two things are alike in numerous respects never shows that they will also be alike in other respects. They may be, but even if they are, the argument from analogy does not prove it; only an investigation of the two things will enable us to discover whether they are alike in the new respect. If the two things are very similar in a large number of respects, it may be more likely that they are similar in the new respect; since lions and leopards are very similar in most respects, a characteristic of lions is quite likely to be true also of leopards — but not all characteristics; if all of them were the same, lions would be indistinguishable from leopards. Even in cases where the two things are very similar, the argument from analogy is still inconclusive." (Hospers, An Introduction to Philosophical Analysis, p. 233.) An argument from analogy may create an exceedingly high degree of probability, but never conclusive proof. At best, analogy is only a makeshift for complete induction — for scientific generalization. And yet human affairs are so pressing and so complicated that sometimes men cannot wait until the process of induction has provided even an imperfect generalization. (Foster, Essentials of Exposition and Argument, pp. 81-2.)
On false analogies versus imperfect analogies in science...
"We have seen that analogy is a fertile source of scientific hypothesis. An analogy or resemblance which is only apparent, not real, is called a false analogy. The points of similarity are not due to the operation of some common cause. Hence, an hypothesis based on such an analogy will be misleading, and must be abandoned ; and this often happens in scientific research. Or, again, the observed analogy may indeed be real, but may have been assumed by the inquirer to be more, or less, extensive than it really is; he may misinterpret it and extend its scope unduly in one direction, or fail to apprehend its real application in another direction. An analogy whose scope and weight are thus wrongly estimated, may be called an imperfect analogy; the hypothesis based upon it will need to be remoulded before it can be verified, and so transformed into a law. This, too, frequently occurs in science: indeed it may be regarded as the usual procedure in inductive research. Non-observation of operative influences is the most frequent cause of imperfection in our analogies." (Coffey, The Science of Logic, p. 331.)
On the value of arguments from analogy...
The worth of an Argument by Analogy depends on the importance of the resemblances on which it is based, and the corresponding non-importance of the differences between the two objects concerned. The resemblances must be essential, the differences unessential. By this we mean that, if the argument is to be cogent, the properties which the two objects (or classes) A and B have in common must be closely related to the problematic property P, while their points of difference must be but loosely connected with it. We must not treat Analogy as though it were a question of Enumeration, and argue as if the strength of the analogical argument depended on the ratio of the number of points of resemblance to the number of points of difference. Mere counting of the points of resemblance and of difference is of little use. (Gibson & Klein, The Problem of Logic, pp. 359-60.)
On analogies that are only wrong in part...
"When an analogy leads to a hypothesis which is afterwards found to be only partially true, and, therefore, to need modification, it is because the force of the analogy has been wrongly estimated. The analogy is present, and really suggests a hypothesis of this general character. But the points of identity have been allowed too much weight relatively to the points of difference with which they are bound up, and, as a consequence, the hypothesis is found to break down in detailed application." (Welton, A Manual of Logic, p. 267.)
On the potentially momentous costs of making false analogies in real life decisions...
"Another reason why a society may fail to anticipate a problem involves reasoning by false analogy. When we are in an unfamiliar situation, we fall back on drawing analogies with old familiar situations. That's a good way to proceed if the old and new situations are truly analogies, but it can be dangerous if they are only superficially similar. ... A tragic and famous example of reasoning by false analogy involves French military preparations from World War II. After the horrible bloodbath of World War I, France recognized its vital need to protect itself against the possibility of another German invasion. Unfortunately, the French army staff assumed that a next war would be fought similarly to World War I, in which the Western Front between France and Germany had remained locked in static trench warfare of four years. Defensive infantry forces manning elaborate fortified trenches had been usually able to repel infantry attacks, while offensive forces had deployed the newly invented tanks only individually and just in support of attacking infantry. Hence France constructed and even more elaborate and expensive system of fortification, the Maginot Line, to guard its eastern frontier against Germany. But the German army staff, having been defeated in World War I, recognized the need for a different strategy. It used tanks rather than infantry to spearhead its attacks, massed the tanks into separate armored divisions, bypassed the Maginot Line through forested terrain previously considered unsuitable for tanks, and thereby defeated France within a mere six weeks." (Diamond, Collapse, p. 423.)