Logical ReasoningDifficulty: Hard

PT12 S1 Q24 Explanation

Until recently it was thought

A free, expert breakdown of this official LSAT Logical Reasoning question.

TopicsFlaw

Keep going in LSAT Lab

  • 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

Start practicing free

Free to start

Full official LSAT questions are available through LawHub. This page provides LSAT Lab's explanation, strategy, and review tools without republishing the full official question.

Stimulus

Until recently it was thought that ink used before the sixteenth century did not contain titanium. However, a new type of analysis detected titanium in the ink of the famous Bible printed by Johannes Gutenberg and in that of another fifteenth-century Bible known as B-36, though not in the ink of any fifteenth-century Vinland Map can no longer be regarded as a reason for doubting the map’s authenticity.

What this question is testing

Flaw

The Two Moves

The author makes two claims from one finding. First: titanium ties B-36 to the Gutenberg Bible — they are the only two with titanium, so they were probably made by the same printer. Second: it is now fine if the Vinland Map has titanium in its ink, because titanium use existed in the 15th century.

Evaluate

Spot the tension. The first move only works if titanium use was extremely rare — otherwise sharing titanium would not be a meaningful link (lots of fifteenth-century books would have it). The second move only works if titanium use was not extremely rare — otherwise a third document with titanium would still be suspicious.

So the same fact about titanium has to be "very restricted" (for B-36) and "not so restricted" (for the Vinland Map). It cannot be both at once.

Goal

The right answer should identify this contradiction in how restricted titanium use is treated.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
24.

The reasoning in the passage is vulnerable to criticism on the

Answer choices

  1. Correct53% picked this

    the results of the analysis are interpreted as indicating that the use of titanium as an ingredient in fifteenth-century ink both was,

    Why this is right

    This nails the contradiction. To support B-36 being printed by Gutenberg, the author must treat titanium use as extremely restricted — so restricted that two books sharing it must come from the same printer. To absolve the Vinland Map, the author must treat titanium use as not so restricted — common enough that another document with titanium can still be authentic. Both inferences cannot stand on the same set of facts. The argument's reasoning is exactly that contradiction.

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

  2. Out of Scope5% picked this

    if the technology that makes it possible to detect titanium in printing ink has only recently become available, it is unlikely that printers or

    What 15th-century printers knew about their ink's composition is not a premise the argument relies on. The argument is about what we can now infer from chemical analysis — not what people in the 15th century were aware of. Even if the author had to address this, it would not undermine the argument's logic.

  3. Bad Description34% picked this

    it is unreasonable to suppose that determination of the date and location of a document’s printing or drawing can be made solely on the

    The argument does not claim that documents can be dated solely based on a single element. It uses titanium as one piece of evidence in a larger picture. This answer attacks a stronger claim than the author actually made — and even if true, it does not capture the actual flaw, which lies in the contradictory uses of the titanium evidence.

  4. Out of Scope2% picked this

    both the B-36 Bible and the Vinland Map are objects that can be appreciated on their own merits whether or not the precise date

    The argument is not about whether the documents can be appreciated apart from their date. It is about how the titanium finding bears on dating and authorship. Whether or not these documents can be enjoyed without that information is irrelevant to the reasoning being evaluated.

  5. Out of Scope7% picked this

    the discovery of titanium in the ink of the Vinland Map must have occurred before titanium was discovered in the ink of the

    The order in which titanium was discovered in different documents is irrelevant to the logic of the inferences drawn. The argument's reasoning does not depend on which discovery came first; it depends on what those discoveries collectively imply, and the flaw is in the contradictory implications, not the timeline of discoveries.

Continue the review in LSAT Lab

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

Save and practice this skill
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