Self-study
Support A certain experimental fungicide causes no harm to garden plants, though only if it is diluted at least to ten parts water to one part fungicide. █████████ ████ █████████ ██ █████ ██ ██ ██ █████████ ███████ ███████ ██████ ████ ██ ███ ███ ████████ ██ █████████ ██ ██████████ ████ ████ ███████ ████ ████ ██████████ ██ ████ ██ ██ ██ ████████████ ████████ ████████ █ █████ ██ ███████████ ███████ ██████ ████ ████ ██████ ████ ████████ ██ ████ ██ ███████ ███ ███████
Argument Summary
Two premises about the experimental fungicide:
Safety: The fungicide doesn't harm garden plants, but only when diluted to at least 10 parts water to 1 part fungicide. Anything more concentrated than that ratio is harmful.
Effectiveness: The fungicide can completely eliminate powdery mildew from rose plants.
From these, the author concludes that the fungicide, as long as it's sufficiently diluted, provides a means of eliminating powdery mildew from rose plants without risking harm to the plants.
Effective at What Concentration?
The premises tell us what level of dilution is required for safety. But notice that they don't tell us whether that level of dilution is sufficient for effectiveness. We know the fungicide can be effective...but at what level of dilution? We don't know.
MORE CONCENTRATED THAN 10:1
Safe? No
Effective? Maybe (premises don't say)
Effective? Maybe (premises don't say)
10:1 OR MORE DILUTE
Safe? Yes
Effective? ???
Effective? ???
The conclusion needs a "yes" in the right column. The premises don't establish it.
Imagine a scenario where the fungicide only works at very strong concentrations, say 1:1 (one part water, one part fungicide). At that strength, it would eliminate powdery mildew, but it would also harm the plants. There would be no dilution that's both safe and effective.
For the conclusion to follow, the fungicide has to actually work at the safe dilutions. The argument needs the fungicide to be effective at concentrations of at least 10:1.
15.
Which one of the following ██ ██ ██████████ ██ █████ ███ ████████ ████████
a
There is not ██ ███████████ ███████ ███████ ███████████ ██ ████ ██████████ ███ ███████████ ███████ ██████ ████ ████ ██████ ███████ ███████ ███ ███████
The argument doesn't claim this fungicide is the only way to eliminate powdery mildew without harming roses. It just claims this fungicide is a way. Whether other methods also exist has nothing to do with whether this method works.
b
When the fungicide ██ ████████████ ████████ ██ ████ ███ ███████ ███ ████ ██ ████ ██ ███████ ████████ ██ ██████████ ████████
The conclusion is specifically about not harming the plants. People, animals, and beneficial insects don't matter. Even if the fungicide might end up harming other living things, we have no reason to think harm to people, animals, or beneficial insects would harm the plants. In addition, in case you're thinking that harm to beneficial insects might indirectly harm the plants, we already have a premise telling us that the fungicide "causes no harm to garden plants" at a certain level of dilution. So meeting that level of dilution causes no harm, whether direct or indirect; whatever's going on with insects doesn't affect the fact that the fungicide doesn't harm garden plants at that level of dilution.
c
Powdery mildew is ███ ████ ██████ █████████ ████ ███████ ████ ███████
The argument is specifically about eliminating powdery mildew. The conclusion claims the fungicide can eliminate this particular infection without harming the plants. Whether roses are also susceptible to other fungal infections is irrelevant; those other infections aren't mentioned in the conclusion, and the argument doesn't need to claim anything about them.
d
If a fungicide ██ ██ ██ █████████ ███████ ███████ ██████ ██ ████ ███████ ██ ████ █████████ ███ ███████ ██████ ███████████
(D) provides a general standard: a fungicide must completely eliminate powdery mildew in order to count as "effective" against it. The argument doesn't need that standard. The premise already tells us that this particular fungicide can completely eliminate powdery mildew. The argument is based on that premise, not on any general definition of "effective." Whether "effective" requires complete elimination as a matter of definition doesn't change what we already know about what this fungicide can do.
The negation test confirms this. Suppose (D) is false: a fungicide CAN be effective against powdery mildew without completely eliminating it. Does this hurt the argument? No. The premise still tells us this fungicide can completely eliminate mildew, and that fact stands regardless of how "effective" gets defined.
e
The effectiveness of ███ █████████ ████ ███ ██████ ██ ███ █████ ████ ████████████ ████ ███ ████ ██ ███ █████ ██ ██████
This is necessary in order for the argument to make sense. The premises tell us the fungicide can eliminate mildew, but they don't say at what concentration. The premises also tell us safety requires a dilution of at least 10:1. Imagine if (E) were not true: what if the fungicide does require less than a 10:1 concentration to be effective? Then at safe dilutions (at least 10:1), it can't do the job, and the conclusion that the fungicide provides a safe means of eliminating mildew doesn't make sense, because it wouldn't eliminate mildew. That's why the argument must assume (E).