Which are the errors of relevance within the category of informal errors of argumentation?
Informal errors of argumentation are those that occur without affecting the argument's formal correctness, that is, without creating an invalid argument. Rather, these errors are errors of content.
A subcategory of informal errors is that of errors of relevance. These occur when the explicitly asserted premises are irrelevant to the conclusion, and the link between these premises and the conclusion is made via a false supposition.
We can distinguish the following errors of relevance.
1. Argumentum ad hominem. These arguments commit the error of denying the conclusion of an argument presented by an opponent by avoiding the grounds presented by this and emphasising instead some irrelevant features of the opponent him/herself. We can distinguish three subtypes of this error:
a. Abusive ad hominem - when an opponent's opinion is rejected by an irrelevant appeal to some moral or characterial defficiency of him/her.
Example: 'Mary ...