Fallacies. Flaws in the Structure of an Argument. What are fallacies?. Fallacies are defects in an argument that cause it to be invalid, unsound, or weak. Fallacies can be separated into two general groups: formal and informal . . Formal Fallacies.
Flaws in the Structure of an Argument
1. All humans are mammals. (premise)2. All cats are mammals. (premise)3. All humans are cats. (conclusion)
1. All A are C2. All B are C3. All A are B