Summarize Argument
The author concludes that lower dosages of certain medicines should be taken with grapefruit juice. This is because it’s best to take low dosages of medicine when possible, and grapefruit juice intensifies dosages. Thus, a lower dosage taken with grapefruit juice would act like a normal dosage.
Notable Assumptions
For this to be the “best medical approach,” the author must believe that grapefruit juice is consistent in its chemical composition. If one glass were to have even slightly more of the chemical than another glass, then the approach would be seriously, dangerously flawed.
A
The amount of the chemical in grapefruit juice is highly unpredictable from glass to glass.
Each glass of grapefruit juice isn’t equal. If the concentration of the chemical was significantly higher in one glass, then the medicine would be elevated to a dangerous dosage. This wouldn’t be “the best medical approach” by any standard.
B
Grapefruit juice is less expensive than most of the medicines with which it interacts.
We don’t care about how much grapefruit juice costs.
C
When scientists removed the chemical from grapefruit juice, the juice no longer affected how certain medicines were absorbed.
The author knows this. It’s integral to their argument about how grapefruit juice should be used with low dosages of medicine.
D
The chemical in grapefruit juice works by inhibiting an enzyme in the body that affects how certain medicines are metabolized.
This explains how grapefruit juice interacts with medicines. The author’s argument relies on this mechanism working.
E
Long before the chemical in grapefruit juice was identified, doctors were advising patients who took certain medicines to avoid grapefruit juice.
We don’t care that doctors probably knew that grapefruit juice intensifies medicines. We’re trying to weaken the author’s recommendation.
Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that the heating up of the squirrel’s tail probably helps to repel rattlesnakes. This is based on the fact that adult squirrels harass threatening rattlesnakes by wagging and puffing up their tails. In addition, the tail heats up, and rattlesnakes can detect body heat.
Notable Assumptions
The author assumes there isn’t another explanation for why the squirrel’s tail heats up when a squirrel harasses a rattlesnake.
A
Rattlesnakes do not have the ability to increase the temperature of their tails.
We’re talking about the purpose of squirrels heating up their own tails. Rattlesnake tails are irrelevant.
B
Squirrels puff up their tails and wag them when they attempt to attract the attention of other squirrels.
This has no clear connection to the heating up of a tail and whether it’s related to repelling rattlesnakes.
C
Rattlesnakes react much more defensively when confronted with a squirrel whose tail is heated up than when confronted with one whose tail is not.
This strengthens the hypothesis by making it more plausible. The heating in a squirrel’s tail seems to make the rattlesnake feel more threatened, which is what we’d expect if the heat played a role in repelling snakes.
D
The rattlesnake is not the only predator of the California ground squirrel that causes it to engage in harassing behavior as a defensive mechanism.
The argument is about the role of a heated tail in repelling rattlesnakes. Other predators don’t strengthen the connection between a heated tail and repelling rattlesnakes.
E
Mammals such as the California ground squirrel have no organ for sensing infrared energy.
We’re talking about the effect of a squirrel’s heated tail on rattlesnakes. Whether squirrels can detect heat doesn’t matter, because we know that rattlesnakes can detect heat.
Summarize Argument: Counter-Position
The critic concludes that Fillmore’s argument should be rejected because Fillmore benefits from convincing parents that watching TV is not harmful to children.
Identify and Describe Flaw
This is the cookie-cutter “ad hominem” flaw, where the author attacks the source of an argument rather than the argument itself. Here, the critic argues that Fillmore’s argument should be rejected simply because the argument benefits Fillmore. She attacks Fillmore instead of giving any reason to believe that Fillmore’s conclusion is false.
A
It takes a necessary condition for something’s being harmful to be a sufficient condition for being harmful.
This is the cookie-cutter flaw of confusing necessary and sufficient conditions. The critic doesn't make this mistake. Her argument doesn’t rely on conditional logic; instead, it relies on an attack against Fillmore.
B
It concludes that something is true merely on the grounds that there is no evidence to the contrary.
The critic concludes that Fillmore’s argument is false merely on the grounds that the argument would benefit Fillmore. The critic never claims that there’s no evidence to contradict her own conclusion.
C
It rejects an argument solely on the grounds that the argument could serve the interests of the person making that argument.
The critic rejects Fillmore’s argument solely on the grounds that it serves the interests of Fillmore. She never provides any evidence to support her conclusion that Fillmore’s argument should be rejected. In other words, she attacks Fillmore himself, rather than his argument.
D
It is based on an appeal to the views of someone with questionable authority on the subject matter.
The critic’s argument isn’t based on an appeal to anyone’s views or authority at all. Instead, it’s based on an attack against Fillmore.
E
It bases its conclusion on claims that are inconsistent with one another.
The critic bases her conclusion on a single claim: that Fillmore benefits from convincing parents that watching TV is not harmful to children. This claim may not support her conclusion well, but it doesn’t contradict any other claim.