Quote:you can't prove a negative.
I keep running across that cliche . I think it's wrong.
Falsifiability is used constantly in science. IE proving X is not the case.
The logician does the same think when he uses a rule of inference to infer X is NOT the case[/quote].
A weakness of ALL arguments not supported by evidence is that few people seem aware of a basic principle of logical inference.: A logically valid argument MAY be true, but truth is not a condition.
[/quote]A rule of inference needn't preserve any semantic property such as truth or validity.[quote]
http://en.wikipedia.org/wiki/Rules_of_inference