Excavations of the Roman city of Sepphoris have uncovered numerous detailed mosaics depicting several readily identifiable animal species : a...

GMAT Critical Reasoning : (CR) Questions

Source: Official Guide

Critical Reasoning

Assumption

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Excavations of the Roman city of Sepphoris have uncovered numerous detailed mosaics depicting several readily identifiable animal species : a hare, a partridge, and various Mediterranean fish. Oddly, most of the species represented did not live in the Sepphoris region when these mosaics were created. Since identical motifs appear in mosaics found in other Roman cities, however, the mosaics of Sepphoris were very likely created by traveling artisans from some other part of the Roman Empire.

Which of the following is an assumption on which the argument depends?

The Sepphoris mosaics are not composed exclusively of types of stones found naturally in the Sepphoris area.

There is no single region to which all the species depicted in the Sepphoris mosaics are native.

No motifs appear in the Sepphoris mosaics that do not also appear in the mosaics of some other Roman city.

All of the animal figures in the Sepphoris mosaics are readily identifiable as representations of known species.

There was not a common repertory of mosaic designs with which artisans who lived in various parts of the Roman Empire were familiar.

Solution

Passage Analysis:

Text from Passage	Analysis
Excavations of the Roman city of Sepphoris have uncovered numerous detailed mosaics depicting several readily identifiable animal species : a hare, a partridge, and various Mediterranean fish.	What it says: Archaeologists found detailed animal mosaics in the Roman city of Sepphoris showing specific creatures What it does: Sets up the basic discovery that will be examined What it is: Archaeological finding Visualization: Sepphoris excavation site with 15-20 detailed mosaics showing hares, partridges, and Mediterranean fish
Oddly, most of the species represented did not live in the Sepphoris region when these mosaics were created.	What it says: The animals shown in the mosaics weren't actually found in that area back then What it does: Creates a puzzle - why would local artists depict animals they'd never seen? What it is: Author's observation Visualization: Sepphoris region (local animals: desert creatures, local birds) vs. Mosaic animals (hares, partridges, Mediterranean fish) - 70-80% of mosaic animals don't match local wildlife
Since identical motifs appear in mosaics found in other Roman cities, however, the mosaics of Sepphoris were very likely created by traveling artisans from some other part of the Roman Empire.	What it says: The same animal designs show up in mosaics across different Roman cities, so traveling craftsmen probably made them What it does: Proposes a solution to the puzzle by connecting the evidence to a logical explanation What it is: Author's conclusion Visualization: Roman Empire map showing Sepphoris + 5-6 other Roman cities, all with identical animal motifs, with arrows showing traveling artisans moving between cities

Argument Flow:

We start with an archaeological discovery, then learn about a puzzling mismatch between the animals shown and local wildlife, and finally get an explanation based on similar patterns found elsewhere in the Roman Empire.

Main Conclusion:

The Sepphoris mosaics were very likely created by traveling artisans from some other part of the Roman Empire.

Logical Structure:

The argument uses the combination of two pieces of evidence - the mismatch between depicted animals and local species, plus the identical motifs found in other Roman cities - to support the conclusion that traveling artisans created these mosaics.

Prethinking:

Question type:

Assumption - We need to find what the argument takes for granted. If we negate the assumption, the conclusion should fall apart while keeping all the facts in the passage intact.

Precision of Claims

The argument makes specific claims about identical motifs appearing across Roman cities and concludes these were made by traveling artisans. We need assumptions that bridge the gap between evidence and conclusion.

Strategy

Look for gaps in the logical chain from evidence to conclusion. The argument jumps from 'identical motifs in different cities' to 'traveling artisans made them.' What must be true for this leap to work? We'll identify assumptions that, if false, would break the conclusion while keeping the stated facts true.

Answer Choices Explained

The Sepphoris mosaics are not composed exclusively of types of stones found naturally in the Sepphoris area.

This focuses on the materials used to create the mosaics rather than the logical connection between identical motifs and traveling artisans. Whether the stones were local or imported doesn't affect the argument about who created the designs. The conclusion about traveling artisans is based on design patterns, not material sourcing. This isn't what the argument depends on.

There is no single region to which all the species depicted in the Sepphoris mosaics are native.

The argument doesn't require that no single region contains all the depicted species. Even if there were one region with all these animals, the key point is that Sepphoris itself lacked most of these species, and the identical motifs across cities still needs explanation. This doesn't address the core logical gap about how identical designs appeared everywhere.

No motifs appear in the Sepphoris mosaics that do not also appear in the mosaics of some other Roman city.

This actually strengthens beyond what's needed and isn't an assumption the argument requires. The argument only needs some identical motifs to exist across cities (which is stated), not that ALL motifs in Sepphoris appear elsewhere. The conclusion works fine even if some Sepphoris motifs were unique.

All of the animal figures in the Sepphoris mosaics are readily identifiable as representations of known species.

This restates information already given in the passage rather than providing a necessary assumption. We're told the species are 'readily identifiable,' so this is already established fact, not something the argument assumes. Additionally, this doesn't bridge the logical gap between identical motifs and the traveling artisans conclusion.

There was not a common repertory of mosaic designs with which artisans who lived in various parts of the Roman Empire were familiar.

This captures the crucial assumption. If there WAS a common repertory of designs available throughout the Roman Empire, then local artisans everywhere could access the same standardized patterns, easily explaining why identical motifs appear in different cities without needing traveling artisans. For the traveling artisans conclusion to work, we must assume such a shared design collection didn't exist - otherwise the premise about identical motifs wouldn't uniquely point to traveling artisans as the explanation.

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