Bottom-up justification:

Definition Example
An argument of the following form. “a” has the positive quality “x” and belongs to the group “A”. Therefore “A”s have “x”. My neighbor is a banker, and a really nice guy. Therefore, bankers are nice guys.
Also known as: a dicto simpliciter ad dictum secundum quid / faulty generalization
A more detailed treatment of this fallacy can be found on the supplementary Inductive Errors page.

Case Study One

If a convenience store clerk successfully disarms a would-be robber, this is not evidence that confronting robbers is the best policy. A much larger sample of cases would be necessary before any inductive conclusion can be made.

Case Study Two

If your friend wins the lottery after entering a number based on his birthday and weight, this is not evidence that combining a participant’s birthday and weight will yield a number that is in any way connected to a winning lottery number.

Case Study Three

When confronted with statistical data that smoking is harmful, claiming that your smoking 105-year-old uncle disproves the statistics is a bottom-up justification fallacy.

Case Study Four

If, when shown statistical evidence that acquiring a university degree increases your chances of acquiring a satisfying carreer, you invoke successful college drop-out Bill Gates in an attempt to invalidate the statistics, you have committed the bottom-up justification fallacy.

Keep in mind that a fallacious argument does not entail an erroneous position.

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