Arguing from Ignorance

Common sense is our most basic fall-back when confronted by things outside our understanding. My boss likes to call it the "sniff test." Does some knew information conform to what we already know? If it does not, we're likely to reject it; if it does, we're more likely to accept it. Rejecting an argument based on a personal failure to understand is the argument from ignorance (specifically an argument from personal incredulity). That argument goes something like this:

• I don't understand a.
• Therefore no one can understand a, and therefore a must be false.

Stated succinctly, the argumentum ad ignorantiam goes:

A premise is true only because it has not been proven false, or is false only because it has not been proven true.

That level of sophistication (or lack thereof) may be fine when filtering out the mental cruft of daily life, but when it comes to legal analysis, common sense is insufficient. Instead, a position must be backed up by fact and law. However, the common-sense filtering system may be important to determine which of many arguments to spend the time refuting.