The date of the Rimienti World Map, drawn in Italy, is unknown. The map accurately depicts the coastline of western Africa down to the Cape of Good Hope, near Africa’s southern tip. In 1488 Portuguese explorers became the first Europeans to reach the Cape. Since it would have taken at least a year for their information to be brought back to Europe and incorporated into maps, the Rimienti World Map could not have been made before 1489.
Which of the following is an assumption on which the argument depends?
- A. Portuguese authorities generally tried to keep information about Portuguese voyages secret for as long as possible.
- B. A map as complicated as the Rimienti World Map would have required at least half a year for a professional cartographer of the 1400’s to complete.
- C. It would not have taken more than a year for geographical information to travel from Portugal to Italy.
- D. Italian cartographers did not get the information for the Rimienti World Map directly from African sources.
- E. No accurate map of any parts of the coastline of western Africa appeared before the Rimienti World Map.
Solution
Passage Analysis:
| Text from Passage | Analysis |
| The date of the Rimienti World Map, drawn in Italy, is unknown. | What it says: We don’t know when this Italian map was made What it does: Sets up the mystery we’re trying to solve What it is: Author’s statement of the problem |
| The map accurately depicts the coastline of western Africa down to the Cape of Good Hope, near Africa’s southern tip. | What it says: The map shows Africa’s coast very precisely, including a specific southern location What it does: Gives us a crucial clue about what’s on this mystery map What it is: Author’s description of map content Visualization: Map of Africa with detailed coastline marked down to the southern tip |
| In 1488 Portuguese explorers became the first Europeans to reach the Cape. | What it says: Portuguese were the first Europeans to get to that southern tip of Africa in 1488 What it does: Establishes a key timeline that connects to the map’s content What it is: Historical fact Visualization: Timeline: 1488 – Portuguese reach Cape of Good Hope |
| Since it would have taken at least a year for their information to be brought back to Europe and incorporated into maps, the Rimienti World Map could not have been made before 1489. | What it says: News takes time to travel, so the map couldn’t exist before 1489 What it does: Combines previous facts to reach a conclusion about the map’s earliest possible date What it is: Author’s conclusion Visualization: Timeline: 1488 (Portuguese reach Cape) ā 1 year delay ā 1489 (earliest possible map date) |
Argument Flow:
The argument starts with a mystery (unknown map date), gives us a clue (the map shows accurate African coastline), provides historical context (Portuguese reached the Cape in 1488), then combines these facts with a timing assumption (information transfer takes a year) to establish the earliest possible date for the map.
Main Conclusion:
The Rimienti World Map could not have been made before 1489.
Logical Structure:
The argument assumes that since the map accurately shows the Cape of Good Hope, and Europeans first reached there in 1488, and it takes at least a year for geographic information to travel back and get put into maps, then 1489 is the earliest the map could exist. The logic depends on the assumption that the mapmaker needed European exploration data to create the accurate coastline.
Prethinking:
Question type:
Assumption – We need to find what the argument takes for granted but doesn’t explicitly state. The argument concludes the map couldn’t have been made before 1489, so we need to identify unstated beliefs that must be true for this conclusion to hold.
Precision of Claims
The argument makes specific claims about timing (1488 for Portuguese arrival, at least 1 year for information transfer, 1489 as earliest map date) and geographic accuracy (the map shows the Cape of Good Hope correctly). We need assumptions that bridge these factual claims to support the conclusion.
Strategy
For assumption questions, we identify ways the conclusion could be falsified while respecting the given facts. The argument assumes the Portuguese were the ONLY source of Cape information for European mapmakers. We’ll think of what must be true about information sources, timing, and the map’s creation process.
Answer Choices Explained
A. Portuguese authorities generally tried to keep information about Portuguese voyages secret for as long as possible.
This discusses Portuguese authorities keeping voyage information secret. However, the argument’s timeline is based on logistical constraints (how long it takes for information to travel and be incorporated), not on deliberate secrecy. Whether Portugal tried to keep information secret doesn’t affect the core reasoning about when the map could have been created. The argument would work the same way regardless of Portuguese secrecy policies.
B. A map as complicated as the Rimienti World Map would have required at least half a year for a professional cartographer of the 1400’s to complete.
This focuses on how long it takes to physically create a map. While the argument mentions time for information to be ‘incorporated into maps,’ the bottleneck identified is information travel time, not map creation time. Even if map creation took half a year, this doesn’t bridge the gap in the argument’s logic about information sources. The argument could work whether maps take weeks or years to create.
C. It would not have taken more than a year for geographical information to travel from Portugal to Italy.
This states that geographical information wouldn’t take MORE than a year to travel from Portugal to Italy. This actually works against being an assumption since the argument only requires that it takes ‘at least a year’ – if it took longer, that would only strengthen the conclusion that the map couldn’t be made before 1489. The argument doesn’t depend on any maximum time limit.
D. Italian cartographers did not get the information for the Rimienti World Map directly from African sources.
This is the correct answer. The argument assumes Italian cartographers needed to wait for Portuguese exploration information to accurately depict the Cape of Good Hope. If we negate this assumption – if Italian cartographers COULD get the information directly from African sources (traders, existing African knowledge, etc.) – then the entire timeline collapses. They wouldn’t need to wait for Portuguese explorers at all, and the map could have been created well before 1489. This assumption is essential for the argument’s conclusion to hold.
E. No accurate map of any parts of the coastline of western Africa appeared before the Rimienti World Map.
This claims no accurate map of western Africa’s coastline appeared before the Rimienti World Map. However, the argument is specifically about dating the Rimienti map based on the Cape of Good Hope depiction, not about whether other maps existed. The existence or non-existence of other maps doesn’t affect the logical connection between Portuguese exploration and when this particular map could have been created.
