Descriptive assumptions --
Prescriptive or value assumptions --
Illustrating Descriptive Assumptions
We know that, by itself, a reason cannot support a conclusion; the reason must be connected to the conclusion by certain other (frequently unstated) ideas.
CAUTION: Remind yourself that the argument holds together in a certain way only because certain assumptions were made.
Clues for Locating Assumptions
Your job in finding assumptions is to reconstruct the reasoning by filling in the missing gaps.
Applying the Clues
CAUTION: If we have some questions about the accuracy of the descriptive assumption, ask for justification. If inadequate explanations is the only respons, reject the argument as unconvincing.
Avoiding Analysis of Trivial Assumptions
After locating assumptions you must make an attempt to determine whether the assumptions make sense.
If you have some basis for doubting the appropriateness of the assumption, then it is fair to reject the reason or conclusion that was propped up by that assumption.
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