It seems to me that you’re trying to bridge the gap between arguments which are logically false no matter what (A implies B, therefore B implies A) and arguments which require some knowledge of the world in order to evaluate them.
The argument about ghosts is a fallacy if there’s no solid evidence of any ghosts ever. The argument about the safety of a drug is stronger than the ghost argument (though weaker than a good argument) if safe drugs are known to exist. By bringing in more of the real world (that drug’s been carefully tested, it’s been in use for a long time, and no serious side effects have been observed), you’ve got as good an argument as is possible for the drug being safe.
A) I’ve often drunk alcohol, and never gotten drunk. Therefore alcohol doesn’t cause intoxication.
B) I’ve often taken Acme Flu Medicine, and never gotten any side effects. Therefore Acme Flu Medicine doesn’t cause any side effects.
The real world strikes again! These arguments can only be evaluated if you know something about human variation.
It seems to me that you’re trying to bridge the gap between arguments which are logically false no matter what (A implies B, therefore B implies A) and arguments which require some knowledge of the world in order to evaluate them.
The answer to this observation and the seeming impossibility of bridging the gap, I think, is that the pure formal validity of an argument manifests only in artificial languages. The “fallacies” are part of the study of informal reasoning. But as such, their acceptability always depends on background knowledge. The strictures of “informal logic” should be applied (and in ordinary rational discourse, are implied) in a more graded, Bayesian fashion; but they were developed assuming a closer relation than really exists between formal and informal reasoning.
It seems to me that you’re trying to bridge the gap between arguments which are logically false no matter what (A implies B, therefore B implies A) and arguments which require some knowledge of the world in order to evaluate them.
The argument about ghosts is a fallacy if there’s no solid evidence of any ghosts ever. The argument about the safety of a drug is stronger than the ghost argument (though weaker than a good argument) if safe drugs are known to exist. By bringing in more of the real world (that drug’s been carefully tested, it’s been in use for a long time, and no serious side effects have been observed), you’ve got as good an argument as is possible for the drug being safe.
The real world strikes again! These arguments can only be evaluated if you know something about human variation.
The answer to this observation and the seeming impossibility of bridging the gap, I think, is that the pure formal validity of an argument manifests only in artificial languages. The “fallacies” are part of the study of informal reasoning. But as such, their acceptability always depends on background knowledge. The strictures of “informal logic” should be applied (and in ordinary rational discourse, are implied) in a more graded, Bayesian fashion; but they were developed assuming a closer relation than really exists between formal and informal reasoning.