Reading Comprehension

PT144 · S1 · P4 · Q25 Karl Popper

A free, expert breakdown of this official LSAT Reading Comprehension question.

  • Save & drill this skill build targeted practice sets from questions like this one

  • Video walkthroughs watch every question solved step by step

  • 81 official LSATs as questions, timed sections & full-length tests

Passage A

Passage A

The author presents and mildly critiques the ideas of Karl Popper regarding positive and negative evidence.

She starts out acknowledging the merits of his contribution. Negative evidence is definitely more powerful than positive evidence, since negative evidence has the power to prove a theory wrong, whereas positive evidence only shows that "so far, it's always been correct".

The rest of the first paragraph involves a series of attributions to Popper. Frequently, if an author is taking pains to separate someone else's ideas from her own, it's because a disagreement is around the bend. We can also see a negative attitudinal marker with the work "hyperbolic", which means exaggerating to an unrealistic degree.

Paragraph 2 delivers on our suspicions with a "However" author pivot. The second paragraph stresses that Popper goes overboard in acting like , since in the real world it's messier than that.

Testing scientific theories (to see whether we get positive or negative evidence, i.e. matching the predictions vs. not-matching the predictions) means assuming that other theories are correct, that your measuring instruments are working correctly, and potentially other assumptions.

So when negative evidence is found, it isn't immediately clear what that's telling us: it could be telling us, as Popper is thinking, that the theory we're testing is wrong but it could just be that one of our other theories is wrong, or that something went awry with the measurement.

Passage B

As we start the second passage, we're listening attentively for the first signs of Overlap. In the second sentence, we see "auxiliary assumptions" (which to me sticks out, because prior to Passage A, I had never heard the expression "auxiliary premises" before).

So we pause and possibly re-read that part of Passage A to dial in the meaning / significance of auxiliary assumptions to Passage A:

when a measurement doesn't match Theory A's predictions, - maybe Theory A is wrong - maybe an auxiliary assumption is wrong (e.g. Theory B is wrong. Idea X is wrong. Our instruments failed)

Passage B then takes us through two different examples.

Uranus Mercury

Measure U's orbit M's orbit doesn't didn't match didn't match match Newton's theory Newton's theory theory Reason for negative evidence

Aux. assump = wrong. Theory = wrong. We'd assumed there At first we thought weren't any planets aux assump of no nearby Uranus, planets near M was because we wrong, but once hadn't found Einstein's math Neptune yet worked, we found out Newt's theory was wrong.

25.

In passage B's description of the developments leading to the rejection of Newton's theory of gravity, which one of the following astronomical bodies plays a role most analogous to the black swan discussed in passage A?

  1. Correct

    Mercury

    Why this is right

    Mercury's weird orbit was the negative evidence that showed us Newton's theory was wrong, just as a black swan was the negative evidence that showed us "all swans are white" was wrong.

    Skill tested: Analogy · how this choice captures the passage's function is the move to repeat next time.

    65% picked this

  2. Uranus

    Unrelated to Goal

    Uranus didn't show us that Newton's theory was wrong. Uranus showed us we were wrong to make the auxiliary assumption that "there are no planets near Uranus".

    5% picked this

  3. Neptune

    Unrelated to Goal

    Neptune didn't show us that Newton's theory was wrong. Neptune showed us we were wrong to make the auxiliary assumption that "there are no planets near Uranus".

    28% picked this

  4. Venus

    Unrelated to Goal

    Venus didn't even appear in either passage.

    1% picked this

  5. the sun

    Unrelated to Goal

    The sun didn't show us that Newton's theory was wrong. Mercury's weird orbit around the sun showed us that.

    1% picked this

Continue the review in LSAT Lab

Save this question, watch the video walkthrough, and drill similar questions in your LSAT Lab account.

LSAT Lab

Turn this review into a targeted study plan.

Save this question, drill more like it, watch the video walkthrough, and track your progress in your LSAT Lab account.

Start practicing free