Logical ReasoningDifficulty: Medium

PT1 S4 Q7 Explanation

When Cortez arrived in Mexico

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

TopicsNecessary Assumption

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Stimulus

When Cortez arrived in Mexico in A.D. 1519, he observed the inhabitants playing a ceremonial game with a rubber ball. The pre-Columbian inhabitants of Mexico began to use rubber around A.D. 1000. Thus, we can be sure between approximately A.D. 1000 and Cortez’ arrival.

What this question is testing

Necessary Assumption

Your task

Find the assumption the argument requires in order for its conclusion to hold.

Common trap

Answers that would help the argument but aren't strictly required (sufficient, not necessary).

Winning move

Negate each choice — the right one breaks the argument when negated.

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

The question
7.

The conclusion reached above depends on which one of the

Answer choices

  1. Too Strong: all1% picked this

    The pre-Columbian inhabitants of Mexico played games on all

    This just takes factual stuff we heard (they were playing a ceremonial game) and inflates it into an incredibly extreme idea: at every single ceremonial occasion ever they played games The author doesn't need to assume that 100% of ceremonial occasions involved playing games. If only 99% of them did, would that change the argument in any way? No.

  2. Too Strong: earliest16% picked this

    The making of rubber balls was one of the earliest uses of rubber by the

    If the game was played with a rubber ball in the year 1000, which was right when inhabitants started using rubber, then sure the rubber ball would be one of the earliest uses. But the author isn't claiming that this game started in 1000. She's only claiming that it started between 1000-1519, For all she knows/cares, the game didn't start until the year 1400, which certainly wouldn't make the rubber ball one of the earliest uses of rubber.

  3. Out of Scope: popular1% picked this

    The ceremonial game referred to was popular

    It doesn't matter to the author's argument whether the game was popular or obscure. Whether it was known throughout Mexico, or only in one village. She's only trying to establish a chronology for when it was invented.

  4. Correct78% picked this

    The game had been played since its inception with a

    Why this is right

    If we negate this, it would say, "This game hasn't always been played with a rubber ball." Thus, at its inception (when the game was invented / when it originated), it may have been played with a ball made of straw or made of leather. That badly weakens the argument, because the author is trying to set the "earliest possible date for this game to exist" at the year 1000 A.D., based on the fact that rubber wasn't used until 1000. But if we say, "hey author -- when this game was originated, it didn't use a rubber ball", then the rubber date of 1000 A.D. is meaningless. In other words, it's possible the game was originated in 800 A.D. with a straw ball, and they later switched to a rubber ball, once rubber started to get used.

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

  5. Unsupported Causality: due to4% picked this

    The dating of the first use of rubber in Mexico was

    We know that Cortez observed inhabitants playing a game with rubber ball in 1519, when he arrived in Mexico. Did the argument imply that Cortez is the reason we know that the first use of rubber was in the year 1000? Not at all. We have no idea how it was learned that the first use of rubber in Mexico was around 1000. Whether the dating of that earliest use was due to Cortez or due to someone else, it wouldn't affect the argument at all.

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