Last week we discussed several logical reasoning flaws that are commonly found on the LSAT, and the fact that many of those flaws have been nicely exemplified by the candidates during the current political season. This week we consider several more examples.
Causal reasoning flaw: assuming a causal relationship where only a correlation has been indicated. Donald Trump has, on more than one occasion, pointed to his extraordinary wealth as evidence of his skills as a businessman. Putting aside the issue of varying definitions of success, Trump certainly has an impressive net worth, and he has obviously made a lot of money over the years. This does not, however, provide irrefutable proof that he deserves all of the credit. Is he the true cause? There are countless other factors that may have contributed to his current fortune; some have asserted that Trump would actually have more money if he had taken his enormous inheritance and simply invested it in an index fund.
When you see this type of error in a logical reasoning stimulus, the right answer tends to provide a description such as "confusing the coincidence of two events with a causal relation between the two." or "assumes a causal relationship where only a correlation has been shown."
Source argument: an attack on the person (or source) rather than on the argument they advance.
Hillary Clinton and her supporters have repeatedly claimed that the Benghazi committee is motivated primarily by the desire to hurt her politically. This assertion was recently given some unwitting support by House Majority Leader Kevin McCarthy, who suggested in an interview that the committee had been intended to hurt Clinton's poll numbers. Regardless, however, this focus on the motives of the source would not be sufficient to dismiss the findings of the committee without consideration.
When yon encounter a source argument on the LSAT, you may see it described as "directed against the proponents of a claim rather than against the claim itself," or "criticizing the source of a claim rather than examining the claim itself."
Numbers and percentages flaws: drawing unjustified conclusions based on lacking numerical evidence.
In a recent congressional hearing, Chaffetz, who is chairman of the House Oversight Committee, chose to use a graph in support of his claims regarding a particular health care provider's expenditures. One issue with the chart that Chaffetz used, however, was that it had no y-axis, rendering the graph somewhat nonsensical, and useless as evidence. Flaws featured on the LSAT are usually not quite so obvious, although flaws surrounding numbers and percentages are not uncommon.
When an LSAT author draws a flawed conclusion from numerical evidence, you may see it described as "the argument confuses an increase in market share with an increase in overall revenue," or "fails to take into account what proportion of the population is involved in the activity discussed."
Errors in assessing the force of evidence: lack of evidence of a position is taken to prove that position is false.
The fact that someone has never had a scandal does not necessarily mean that the person has never done anything that might be described as scandalous. This is not to say that Governor Chafee is guilty of any impropriety (he seems like a very honest man), but just to clarify that a lack of evidence does not entirely disprove.
When you encounter this sort of flawed reasoning on the LSAT, the right answer choice may be characterized as "takes the failure to prove a claim as constituting denial of that claim," or "treats the lack of evidence of a claim as though it disproves the claim."
Again, it's valuable to be familiar with these logical reasoning flaws so that you can quickly recognize them; you will almost certainly see some on your test. Be on the lookout for other such flaws in politics, advertising, and countless other contexts, and for a complete discussion of flaws, pick up a copy of the renowned PowerScore LSAT Logical Reasoning Bible.
Image: Turret Arch through North Window at sunrise at Arches National Park, Moab, Utah, courtesy of Diana Robinson.