21 - Analogical Reasoning
An analogy compares one thing to another, which is often used to describe something that is unknown in comparison to something that is more familiar so that it may be more readily understood.
The author also refers to analogy as a literary device, which is often more subtle and clever in its nature, as well as the use of analogy as a humorous device. These are different to the way that analogy should be used in argumentation, but argument often has a flair for the dramatic.
Analogy or similarity also has less dramatic and more practical aspects:
- We assume that when we replace an item, the new will be as good as the old
- Because we liked brand X ketchup, we will like brand X mustard
- Because it is wrong to break into someone's home, it's also wrong to hack into their computer
- Because we like two people, we assume they will like one another
The danger in analogy is in failing to identify the ways in which two things are actually similar, and the ways in which they are different, that are significant to our conclusion. In some instances, analogy can obfuscate meaning or lead to inappropriate conclusions when this connection is unclear or irrelevant.
Evaluating Analogical Arguments
The author mentions four basic criteria for evaluating an analogy:
- Truth - Are the two things really similar in the way they are described? "An apple is like a rabbit because they are both covered in fur" is not a valid analogy.
- Relevance - Are the properties described at all relevant to the conclusion? "A skewer is like a toothpick because they are both long and sharp at the ends" may be valid, but it has nothing to do with an argument about capital punishment.
- Degree and Diversity - Are there many shared properties of diverse types? In general, the more two things have in common, the stringer the power of an analogy between them (an apple is more like a pear than an orange)
- Disanalogy - Are there also differences that can be compared, or admitted? An analogy is stronger if the dissimilarities are known and noted. It's also noted that pointing out how things are different can support an argument that they are no similar.
Treating Like Cases Alike
Analogical arguments are prominent in legal and moral discussions because there is a sense of equity where an external force (government) creates artificial outcomes. The notion of fair treatment under the law requires that we respect the rights of all people equally, and punishment for similar crimes is similar in degree.
It's noted that this is justice in the abstract rather than the concrete sense - it does always result in equal treatment, but freedom from bias. For example, if there is a federal grant for scholarships, everyone should have an equal chance at getting one - but because the budget is limited, there will be instance where there are more candidates than scholarships. They cannot be treated equally (not every qualified applicant will get a scholarship), but they are at least treated in an unbiased manner (given equal qualifications, a random lottery decides who gets the scholarship).
But as before, we must be cautious to the differences as well as the similarities when stating that two cases are alike - setting conditions for receiving a privilege, or mitigating conditions when meting out punishment, are the result of considering the degree to which two cases that seem alike are dissimilar.