Flaw of the Week

This week’s FOTW can show up in a couple of contexts.  I’ll describe it briefly, then note a couple of past LSAT questions showing how it might turn up.

The gist of it is this – the premises mention two different categories (of people or things), and then the conclusion, without justification, is based on the notion that there is no third (typically a “middle” – I’ll explain) group.

For instance, in one past LSAT question (somewhat changed/paraphrased for simplicity and clarity), the premises note that reading homework isn’t necessary for students who like a topic- they’re going to read about it anyway.  Moreover, reading homework doesn’t benefit students who hate a topic – they’re not going to do it anyway.  The conclusion is that there is no point in teachers’ assigning written homework.  The conclusion, in other words, operates on the notion that there is no third group – the students either love or hate the topic.  But what about students who are indifferent – those who don’t like the subject enough to read about it on their own, but don’t hate it enough to skip homework?  That’s what I mean by a middle group.  Those students would do the reading, but only if it’s assigned.  So there IS a point in assigning such homework.

Another past LSAT question (again, simplified and/or modified) defines some actions as morally good and others as morally bad.  It then describes a certain action and claims that it’s not morally good.  The conclusion is that it’s morally bad.  The flaw, essentially, is that the argument fails to recognize that some actions may be morally neutral.  This one is actually written as an assumption question, but it’s the same notion.

There’s actually a fine line between an assumption question and a flaw question.  For instance, let’s say my argument is, “John went to Yale.  Therefore, John is smart.”  I could write that as an assumption question (correct answer: All students who go to Yale are smart) or a flaw question (correct answer: fails to consider the possibility that some students who go to Yale are not smart). 

What would the correct answers look like in the above past LSAT questions (assuming they were both written as flaw questions)?  It depends…there are different possibilities, but here are a couple of possibilities:

“Fails to consider the possibility that some students neither love nor hate certain topics.”

“Takes for granted that an action that is not morally right must be morally wrong.”

Notice that in the examples there is a jump between the premises and the conclusion.  That’s where flaws happen.  Premises are facts.  They’re evidence presented that for the sake of argument we have to accept as true.  Conclusions are interpretations – that’s where the writer of the passage decides what the evidence means.  That’s where arguments (potentially) go wrong.  You see these sorts of jumps most explicitly in assumption questions, where you might have a premises about students with special education needs, and a conclusion about students with learning disabilities.  But not all students with special education have learning disabilities (blind students, for instance, generally fall into the former, but not the latter, category).  So remember…it’s the conclusion where the flaw “happens.”



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