An ad hominem fallacy, also known as an “argument against the person,” is a logical fallacy in which focus is diverted from the strength of an argument itself to the qualities of the person making the argument. By finding fault with the person making an argument, it is hoped that the argument can be easily discredited without addressing its merits or faults directly. Ad Hominem attacks can be traced back to Aristotle in his Rhetoric, where he observes that “the character of whoever presents an argument is often instrumental in the acceptance of that argument” (1). Tu Quoque arguments, or appeal to hypocrisy, is a type of ad hominem attack in which an attempt is made to discredit a person and his/her argument by showing that the person making the argument has been unable to act in accordance with the position being argued for. For example, if an overweight physician tells somebody to stop eating so much saturated fat because of the health risks, it is tempting to disregard the advice because the person giving it obviously has not been following it. The error in Quoque arguments and in Ad Hominem arguments in general is that an argument’s strength is judged not by the strength or weakness of the argument itself, but on the character of the person making the argument.
(1) Tindale, C. W. (2007). “Ad Hominem Arguments: Fallacies and Argument Appraisal.” Cambridge: Cambridge University Press, 81.