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Analogies
By Charles Parker

Using analogies is a very common practice in everyday life as it helps us to understand and communicate ideas and concepts. Analogies are used in almost every form of human endeavor from linguistics (language), technology, medicine, science, law, theology and most certainly politics. My purpose for this paper is the use of analogies as it pertains to reasoning and logic.

It has been said that the simplest form of inductive reasoning is an “argument by analogy”, which makes a statement or note that two or more things are similar in some respects and from that reasoning it can be applied that they are probably also similar in other aspects. To put it a different way is to say that an analogy is a comparison between two different things in order to highlight some point of similarity.

Few techniques of reasoning are so potentially useful---or so potentially dangerous---as analogy. When we reason by analogy we attempt to advance our position by likening an obscure or difficult set of facts to one that is already known and understood and to which it bears a significant resemblance.

Drawing attention to likenesses can be extremely useful so long as the two things being compared resemble each other in important respects and differ only in trifling ways. If, on the contrary, they are alike in unimportant ways and different in important ways, then there is no valid analogy between them and a fallacy of false analogy (questionable analogy) results. Merely to seize upon some slight similarity as a basis for concluding that what is true of one is also true of the other will usually lead one astray.

However before declaring that someone has offered a “questionable analogy” there needs to be an understanding that there are two types of analogies we may be faced to reason with. One is the explanatory analogies that are merely used to explain something while the second is the argumentative analogies that are used to prove a point. When we argue or reason analogically, we present evidence for a conclusion; when we use an analogy to explain, we merely liken the thing explained to something already familiar.

“Fred likes bananas so he is going to like banana type drinks”

As we go through everyday life it is often difficult to determine if an analogy is intended to explain or to prove; no doubt some are intended to serve both purposes. In any case, as with general explanations, it is hard to separate the mere explanatory nature of an analogy from its power to persuade.

One of the problems with analogies is that every two things resemble each other in an indefinitely large number of ways. Only relevant resemblances count in drawing correct analogies. Second their conclusions are generally weaker than other types of reasoning.

So how does one determine if an analogical statement is good (cogent) or is false (a fallacy). We can start by noting (A) the number of similarities, (B) how relevant is the similarities and (C) the number of dissimilarities. In general the more similarities there are the better the analogy. Also it stands to reason that the fewer dissimilarities the better the analogy. Relevance is more difficult in the comparison because it not something that can be very precise. One must use their best judgment in deciding whether or not some aspect deserves to be considered. Our beliefs and understanding on how things are interrelated are key components to good judgment.

For example the analogy “Lawyers and waiters are the same in that they provide a service to people, take money for that service provided, and use a thought process to accomplish the service provided”. It does not take long to realize this is a false analogy in that the service they provide is entirely different (not relevant), any groups that provide a service are paid, and that all people employ a thought process.

The discipline of Friction Ridge Analysis has seen a number of analogies over the past 8-10 years, from comparing the metal process of an analyst with that of an eyewitness; the methodology of analysis to that of Astrology. One needs to take each analogy and first determine if its purpose is to explain or prove a point. If the analogy is offered to prove a point then great care should be exercised in assessing its merits, faults and relevance before accepting it as a good analogy.

Those within the discipline of Friction Ridge Analysis also provide analogies that I believe are meant to explain a process and not prove a point. For example the error rate in friction ridge analysis is analogous to simple math problems is an explanation and not stated to prove that they spring from the same ground. When people add components to the analogy they are changing its parameters from one of explanation to one of proving a point.

In conclusion analogies are used in everyday life, and as human beings we will still use them as they are an easy form of communicating concepts and ideas. But because they are a form of inductive reasoning we must also be careful in how they are used. The best defense against a distortion of facts is always to sort out those aspects of the analogy that are relevant to an argument and those that are not.

References:

“Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life” 8th, Edition (1998), by Howard Kahane, and Nancy Cavender. Wadsworth Publishing Company

“With Good Reason: An Introduction to Informal Fallacies” 5th Edition (1994), by S. Morris Engel. St. Martin’s Press, New York

http://www.philosophypages.com/lg/e13.htm

Hi Charles,

I found this thread to be 'on the money' in a lot of ways. I like the use of analogies and appreciate your comments/concerns that the use of such should be relevant and reasonable. We dont know how much we have in common with the knowledge and life experiences of the judiciary or the jury. We do know that our knowledge and understanding of fingerprint science has been acquired over a lengthy period and consolidated by actual experience in examinations. The use of analogies helps to create some common ground appreciation of concepts/processes to bring about a mental picture that shapes the logic of our argument. Besides analogies we can also use the concept of 'present sensory experience' where the facilities within the court room become aids to help us explain distances, directions ect. Anyway, liked this one Charles. Thanks also for the many others and I hope you have a great Christmas and New Year. Cheers from oz. Les

Hi Charles & Les

I believe strongly in the use of analogies. An analogy is the use of a familiar concept to explain an unfamiliar concept by comparing the two. You may have heard me in my class or my lectures talk about the "rubber stamp" analogy -- "A fingerprint is like a little rubber address stamp. The little rubber address stamp is permanent and it is unique -- It doesn't change any of the letters or numbers in your desk drawer overnight, and you are the only person in the world with your exact name and address. If your address stamp slips on the paper, it leaves a smear that you may not be able to read. If there is no ink on the stamp, it does not leave a message. If you try to stamp a rough surface like, say, the concrete on the sidewalk outside, you can see where the stamp touched, but you cannot read the message because the texturing of the surface breaks up the letters," etc.

The problem with analogies is that there is no perfect analogy. A smart opposing attorney might try to stretch the analogy to the absurd and thus destroy it. So I agree that the use of analogies to explain what we do is a valid technique, but one has to be careful using them not to take the analogy too far.

Hi Pat,

Yes the rubber stamp analogy is a good one. From a scientific proof point of view the extension of that analogy could leads us into a new dimension of explaining our identifications. The stamp is permanent and unique. It is dimensionally fixed and reproduces the exact pattern of the stamp when placed on a good substrate. The 'matching' of the pattern (latent) to the rubber stamp forms an hypothesis of predictability. That is every feature present in the latent should be exactly positioned to those present in the stamp. By being able to prove the pattern of the stamp we have achieved a form of physical match (geometric dimensions) between the stamp and the latent. Ofcourse in fingerprint science we only witness access to the original stamp when taken as watchhouse prints. The inked prints and the latent prints are matched while the 'source' stamp stays on the finger of the donor. But essentially we are still predicting the design of the pattern on the donor skin with reliable predictability of its sequential and spatial configurations.

Anyway thats as far as I can go must complete jobs before season break. Enjoy your Christmas Pat with all the best to your family and friends. Regards. les

Les and Pat, thanks for the response.

I personally like analogies and probably use them too much.

"That person is busier than a Bulls Tail in Fly Season".

The stamp analogy, the change analogy, the math analogy, the plane analogy are all good as they are an attempt to explain an unknown process with something familiar to the group we are speaking too.

I sometimes have a problem with the analogies that are not meant to explain a process but prove a point. The two I listed in the OP is an example of proof analogies and not an explainatory analogy. Those need to be carefully considered. The one I have heard in this business that drives me nuts is the comparison of the LP Certification process with obtaining a drivers license. I consider that a bad analogy.

Another type of analogy that we as scientist (analyst) need to be careful of is when the analogy is made to past historical events. I have not seen a lot of that in this business but it happens a lot in politics and theology.

Analogies to explain a process is great. Analogies to prove a point; dissect them and look at them very carefully as they will probably not hold water.

Take care and have a happy holidays.

Pat,

I had the bright idea of using that address stamp analogy one time. I didn't know anybody else used it. It back fired on me. The defense attorney capitalized on that and it became the focus of his questions: Aren't rubber stamps made in a factory? Aren't they made by conscious design? Didn't you say fingerprints were random? If you are using conscious design, you can make sure you do not duplicate something, isn't that correct? But if things are random, you have no control over that, do you? And on and on and on. You were right to say the use of analogies is limited and you have to be careful. After that experience, I just explain things straight forward, but in simple terms. I've never had any problems doing it that way.