The folks at LSAC are very good at making a tricky test that (in combination with college GPA) correlates to some degree with first-year law school grades. But creative, they ain’t. As you continue studying for the LSAT, you’ll notice that the test uses the same argument structures over and over.
This is good news for you, the studious test-taker. After all, the more frequently you see these argument structures, the more quickly you’ll be able to recognize them and identify any flaws. However, the full list of argument forms and common flaws can be overwhelming at first blush. With that in mind, here’s a quick rundown of some common argument structures and flaws:
Circular reasoning: One of the answer choices you’ll see frequently on Flaw questions says something like “the argument presupposes what it sets out to prove.” In layman’s terms, this means that the argument’s conclusion is the same as one of its premises, which is what we know as circular reasoning. Circular reasoning is actually one of the more uncommon flaws you’ll see on the LSAT, but it’s important to know because it pops up so frequently as an incorrect answer choice. LSAC is hoping that you, the test-taker, will choose it if you’re not sure exactly what the flaw is, in a “well, this answer choice sounds like it could be plausible” sense. Don’t be fooled! An argument is only truly circular when one of the premises is exactly the same as the conclusion.
Causal arguments: Causality is very, very difficult to prove. Even if it’s 99.9% likely that A caused B, there’s still that pesky 0.1% chance that something else is the true cause. As a result, causal arguments on the LSAT are typically flawed: They generally move from correlation (showing that two things happened at the same time) to causation (assuming that one of those things caused the other).
In order to identify a causal argument, look closely at the conclusion for language such as “resulted in,” “caused,” and so forth. It’s especially important to be able to identify causal conclusions because noticing causal conclusions helps a lot when attacking many Strengthen and Weaken questions, so make sure you’re comfortable spotting causality as it occurs on the LSAT.
Ad hominem attack: This flaw is a classic that you’ll see thrown around a lot. In short, an ad hominem attack occurs when someone criticizes the person making the argument, rather than the argument itself. In real life, this type of argument is used quite frequently – for instance, after seeing that Rush Limbaugh has been married four times, you might throw him some serious side-eye when he starts talking about the sanctity of marriage. However, ad hominem attacks are a flawed response to an argument, as the argument itself could hold water regardless of how scummy or hypocritical the person making that argument may be.
Of course, this is just a sampling of the many argument structures (flawed and valid) that can occur on the LSAT. As you continue your studies, make sure you’re taking some time to notice the common argument structures as they crop up, and soon, you’ll be calling out common flaws and formats like there’s no tomorrow.