Reasoning by Analogy is like Poisoning Kittens
Reasoning by analogy happens all the time: one tries to argue that an ambiguous case should be treated in the same way as a clear case. The consensus on the clear case then transfers to the ambiguous case, and the ambiguity vanishes.
At least that’s the way it’s supposed to work.
The comments of James Hanley’s birth control post tells us how well this actually works at resolving debates. Birth control and guns differ in important ways. Sexual assault differs from getting robbed in at least ten different ways. Taking nude selfies with your phone is not the same as doing various things with your house keys, and no amount of refining or modifying the comparison will suddenly make the analogy insightful for those who disagree with you.
It is impossible to make useful, fully general statements about things as abstract as “things” when all things differ in meaningful ways. Each thing differs from each other thing. That’s why we each thing gets its own name and why some of them are controversial and other are not.
Going back to birth control, buying insurance for an employee that covers some particular thing is different than paying an employee fungible dollars she uses to buy that same thing. And if you think it isn’t different, you still haven’t added to the discussion unless everyone else also already agreed it is the same. By introducing the comparison, you’ve added a separate point of contention that needs to be debated in addition to the initial disagreement.
If you want to defend something, actually defend it, not the cardboard cousin you’re calling its sister.
Here is another example of the perpetually unhelpful analogy:
Corrie’s family is now suing Caterpillar, which made the bulldozer, for damages, on the grounds that Caterpillar knew or should have known that the sale would enable the IDF to commit human-rights violations.
Conservatives like Bainbridge should think about it this way: say a corporation sells sophisticated intelligence-gathering equipment to Fidel Castro’s internal security forces. They, of course, use it to find a pro-democracy activist and then brutally torture her. Is it so unreasonable that the vendor should be held liable?
Selling bulldozers to Israel doesn’t sound that innocuous until we look at the analogy of selling intelligence-gathering equipment to Castro. If you have a problem with that, you should also have a problem with Caterpillar. Right?
Megan McArdle says “no”, and attacks this analogy with, um, another analogy:
If you supply Zyklon B to the Nazis**, you are clearly moral filth whose bankruptcy and disgrace I will not mourn one little bit. On the other hand, if some colonel in Pinochet’s Chile had dubbed himself “El Lápizetero” and terrified prisoners by poking their eyes out with pencils, I would be disinclined to slap a judgement on the manufacturer who sold Chile a couple of gross of Number Two’s.
Bulldozers are, it seems to me, closer to the pencils than the Zyklon B
These arguments are not completely without merit. However, I still hate reasoning by analogy. An analogy creates a new sub-debate as to how much the ambiguous situation resembles the unambiguous one. Where we were once thinking only about bulldozers and Israel, we’re now thinking about bulldozers and Israel and how they relate to Zyklon B, Pinochet, and pencils, not to mention intelligence-gathering equipment, Castro, and the Nazis. You are further from resolution, not closer.
If you make an analogy to a case you believe to be clear, you might be surprised to find it wasn’t as clear as you thought. After all, if it closely resembled a controversial case, maybe we should reconsider just how clear it was to begin with.
The clear case may have a barrel of its own issues. (Bringing up Castro and the Nazis is not usually the way to bring a debate to a quick and speedy closure.)
Instead of analogies, provide actual arguments like Megan does here:
… there is no way that Caterpillar could have reasonably known what the IDF was going to do with that bulldozer, and hence, no grounds for a suit.
Brilliant. That’s the real argument, with direct reference to the objects of concern. No need for outside referents.
Furthermore, don’t accept an analogy as an argument or an explanation. It isn’t one. When they do seem to make things clearer, it is almost always because they leave out pertinent bits of information that were relevant in the ambiguous situation. The reasoner points out all the similarities and skips over the difference between bulldozers and pencils and Zyklon B hoping you will take their word for it that the comparison they picked is a fair one.
The path to clarity is to talk about the thing that needs to be talked about, even if it is messy. Substituting a sanitized analogy makes us feel more comfortable, but is more deceptive than it is illuminative.