PrepTest 126

Incorrect. The conclusion is limited to discussing ball lightning, so this answer is out of scope in discussing other types of lightning.

Incorrect. First, there's no reason to question the observations of the physics professor. Second, if there were, a second person wouldn't magically make the observation indisputable.

Incorrect. If anything, this answer undercuts the conclusion. If ball lightning can result from several different factors, then it's possible that other ball lightning is caused at least in part by the plasma, even if the ball lightning seen by the Physics Professor wasn't.

Incorrect. The argument establishes that the plasma being a factor in ball lightning would mean that ball lightning emits an intense light, so it doesn't matter what causes that light to be emitted.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Sufficient Premise

Stimulus Summary:
Some scientists — Superheated plasma with failed resistance (SHPFR) is a factor in ball lightning (BL)

Physics Professor — SHPFR is a factor in BL → BL emit intense light AND BL rise in air
But the BL that I saw was low intensity and floated horizontally
Therefore — SHPFR is never a factor in BL

Answer Anticipation:
What a question! This is at least one of our instructors's favorite questions—he says that it has many concepts rolled into one (which is why we had him write this explanation).

So let's start with the overall structure—there's an opposing point (Some scientists . . . "), and the viewpoint of the Physics Professor. Since the Physics Professor starts her argument off with, "If this were so . . . , we need to understand that opposing viewpoint—otherwise, we won't know what this" is.

But understanding what they say is a mouthful! That's some scientific jargon if we ever saw it. So let's ignore all the technical mumbo—jumbo and reduce it to some initialisms and the logic—SHPFR (whatever that is) is a causal factor in BL. That's the "this" in the Physics Professor's opening line of, "If this were so, which you can see written into our summary.

And if that were so, there are two things that would be known for sure—the BL would be bright and would float up. The conclusion of the argument, however, is that what the scientists believe is not true—SHPFR is never a factor in BL. In order to reach that conclusion, we need to take the contrapositive of the conditional predicated on the opposing point being correct:
not BL emit intense light OR not BL rise in the air → not SHPFR is a factor in BL

The Physics Professor has seen some BL, and it was of low intensity (not BL emit intense light) and floated horizontally (not BL rise in the air). This should be sufficient to support the necessary condition—not SHPFR is a factor in BL. Isn't that the conclusion? What gives?

The conditional logic works out here, but note that the Physics Professor is basing this on BL that [she] observed"—not all BL. So the Professor's argument has established that the BL she observed wasn't caused by SHPFR, but the conclusion is about all BL ever—SHPFR is "never" a factor in BL. So to justify this conclusion, we need to establish that the ball lightning seen by the Professor is representative of all ball lightning.

Phew, that was a lot! But we know what we're looking for now, so let's go find it.

Answer Explanation:
This answer doesn't appear to address the Professor's ball lightning, or establish that it's representative. However, in discussing "[a]ll" types of ball lightning, that includes the examples seen by the Professor. We showed in our anticipation that the Professor did establish that the plasma wasn't a cause of the ball lightning she saw—in other words, something other than the plasma caused that ball lightning. If all ball lightning has the same cause, then something other than plasma must cause all ball lightning, and the conclusion is justified.

Key Takeaway:
There's a lot to this question, so review it to make sure you understand it! If you do, then you've got a good handle on how the LSAT uses opposing points, conditional logic, and personal samples ("I observed").