Each of the arguments below relies on an implicit foundational assumption essential to establishing its conclusion. Match each argument on the left with the underlying necessary assumption on the right on which it strictly depends.
- Archaeologist: Excavations at an inland cave shelter yielded obsidian projectile points with distinctive impact wear. Because obsidian does not naturally occur anywhere within the shelter's river valley, the cave's inhabitants must have acquired these points through long-distance trade networks.The inhabitants of the inland cave shelter did not travel directly to distant geological deposits to harvest obsidian and manufacture the points themselves.
- Ecologist: A coastal kelp forest suffered severe canopy loss immediately following a sharp decline in local sea otter numbers. Because sea otters prey heavily on sea urchins, which feed on kelp holdfasts, the reduction in otter predation was the cause of the kelp canopy loss.The decline in the sea otter population and the loss of the kelp canopy were not both separate consequences of an external environmental factor.
- Economist: When a luxury watchmaker raised the price of its flagship chronograph by 20 percent, quarterly unit sales rose by 15 percent. Therefore, consumers purchased more units because they perceived the higher price as an indicator of superior prestige.The increase in sales of the chronograph was not entirely driven by a concurrent marketing expansion into newly opened retail territories.
- Art Conservator: Spectroscopic analysis of a Renaissance fresco detected synthetic barium sulfate beneath the apse pigments. Because synthetic barium sulfate was not produced before the nineteenth century, the fresco must be a modern forgery rather than an authentic Renaissance work.The synthetic barium sulfate detected beneath the pigments was not introduced during a nineteenth-century restoration of a genuine Renaissance fresco.
Cevap
Each argument pairs with the defender assumption that rules out an alternative explanation fatal to its conclusion: the obsidian argument pairs with the assumption that inhabitants did not travel to sources directly; the kelp forest argument pairs with the assumption that a third environmental variable did not cause both events; the chronograph argument pairs with the assumption that territory expansion was not solely responsible for sales gains; and the fresco argument pairs with the assumption that the nineteenth-century compound was not added during a later restoration.
Each correct pairing provides an unstated defender assumption that eliminates an alternative explanation capable of disproving the specific conclusion: direct procurement disproves trade dependency; a shared third cause disproves direct ecological causality; retail expansion disproves consumer price perception; and historic restoration disproves total modern forgery.
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Anahtar Kavram
A necessary assumption is an unstated premise required for an argument's conclusion to hold. Under the Negation Test, negating a truly necessary assumption will fatally undermine the author's conclusion.
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