LR Conditional Reasoning Question #1 - Monetary Systems

[Jon Denning]

Taken from: lsat/viewtopic.php?f=707&t=8298

Must Be True—SN. The correct answer choice is (E)

The stimulus contains a fact set without a conclusion, but the combination of the first two premises yields a conclusion that is then stated in the correct answer. Let us review the stimulus sentence by sentence.

The stimulus opens with a conditional statement that can be diagrammed as:

• MS MKT

Note that the necessary indicator “only” modifies “marketplaces” and thus “marketplaces is the necessary condition. The next sentence states that Mesopotamian cities of the fourth century B.C. did not have marketplaces, which is the same as indicating that these particular cities did not meet the necessary condition stated in the first sentence:

• Premise 2: MKTMesopotamian

The combination of these two statements immediately yields the inference that Mesopotamian cities of the fourth century B.C. did not have monetary systems. As this inference is restated in answer choice (E), (E) is correct.

Structurally, the two premises in the first two sentences add together to create a conclusion:

• Premise 1: MS MKT
  
  Premise 2: MKTMesopotamian
  
  Conclusion/Answer (E): MSMesopotamian

The last sentence introduces an issue designed to distract you from the inference discussed above. According to the last sentence, Greek cities of that period did have marketplaces, and according to further information provided, since money was traded there some type of monetary system existed.

The question stem requires you to find an answer choice that must be true, and based on the combination of a fact set with conditional reasoning, you should expect some type of contrapositive.

Answer choice (A): This answer choice can be eliminated because of the word “only.” Although the last sentence of the stimulus indicates that money (and thus a monetary system) was present in Greek cities of the fourth century B.C. there is no indication that Greek cities were the “only” such cities to have a monetary system.

Answer choice (B): The stimulus discusses a conditional relationship wherein the presence of a monetary system means that a marketplace must be present. This answer makes a claim about the origins of marketplaces, specifically that monetary systems cause marketplaces to arise. The stimulus contains no information that would support this statement.

Answer choice (C): The stimulus discusses both the Greeks and Mesopotamians, and also states that the Mesopotamians engaged in trade, but the stimulus does not state that the Greeks and Mesopotamians traded with each other.

Answer choice (D): This answer choice discusses an occurrence “after the fourth century B.C.,” but the stimulus was confined to discussing events “through the fourth century B.C.” Hence this answer choice—like the prior three answers—fails the Fact Test and is incorrect.

Answer choice (E): This is the correct answer choice. As discussed above, this answer choice completes the contrapositive begun in the first two sentences.