Ad hominem argument

In logic, an argument ad hominem (from the Latin 'against man') is known as a type of informal fallacy (an argument that, due to its content or context,, is not qualified to support a thesis) which consists of assuming the falsity of a statement taking as an argument who is the issuer of this. To use this fallacy, an attempt is made to discredit the person who defends a position, pointing out a characteristic or unpopular belief of that person, instead of criticizing the content of the argument defending the contrary position.

An ad hominem fallacy has the following structure:

• A affirms B;
• there is something questionable (or it is intended to question) about A;
• B is therefore questionable.

When denouncing this type of fallacy, one must not fall into the error of thinking that because there is an argument ad hominem, B's statement would be true (this is also a fallacy known as an ad logicam argument).). The fact that someone discredits the speaker does not prove anything about the falsehood or truth of what he says.

The fact of insulting a person within an otherwise rational speech does not necessarily constitute an ad hominem fallacy. The fallacy is committed by merely discrediting the person making the claim, and then not criticizing the content of the claim.

An ad hominem fallacy is one of the best-known logical fallacies. Both the fallacy itself and the accusation of having used it (ad logicam argument) are used as resources in real speeches. As a rhetorical technique, it is powerful and is often used—despite its lack of subtlety—to convince those who are moved more by sentiments and accommodating customs than by logical reasons. Thus, not the arguments themselves are attacked, but the person who produces them and, more specifically, their origin, race, education, wealth, poverty, social status, past, morals, family, etc.

For example:

Dialogue between two people

• A: "The State is not guaranteeing the basic needs of all individuals."

• B: "You never had needs, you cannot talk about what the state does."

In this case B attacked A's morality, but said nothing about basic needs. It is then said that the argument used by B is a fallacy, because it does not prove falsehood, but tries to generate the sensation of falsehood.

Example 2:

• A: "The triangles have four sides".

• B: "You never studied geometry. You have no reason for what you say."

Indeed, A's proposition is false, but not because he has not studied geometry, but because the triangle has three sides.

Examples

• "What can a priest know about the children, if he had none?"
• «Turing thinks machines think. Turing is gay. Therefore, machines do not think.” (Sylogism that appears in a letter written by Alan Turing, due to the social rejection he received for being openly homosexual; he was concerned that the attacks on his person were used to disqualify his work in artificial intelligence.)
• "You say this man is innocent, but you are not credible because you are also a criminal. »

Similar fallacies

Similar fallacies exist:

• Argumento ad verecundiam: one tries to prove that something is true because it has prestige who says it.
• Argument ad lazarum: one tries to prove that something is true because the one who says it is poor, or that something is false because the one who says it is rich.
• Argument ad crumenam: one tries to prove that something is true because the one who says it is rich, or that something is false because the one who says it is poor.
• Lack of association: one tries to prove that something is false because the one who says it belongs to a particular group.
• Fake of the scarecrow (lack of straw man) · a new argument that is unrelated is introduced into the conversation, and it is overwhelmed.

Ad hominem in classical literature

The classics called the argument ad hominem with the expression argumentum ex concessions, that is, it uses in its favor the arguments "accepted" » or «granted» (ex concessions) by the interlocutor. It was John Locke, creator of the arguments in ad, who renamed it ad hominem. A well-known example is that of Tito Livio referring to the way in which Hannibal persuaded his men:

Hannibal [after crossing the Alps] used all kinds of exhortations to encourage that confusing mixture of men who had nothing in common, language, customs, laws, weapons, suits, or appearance or interests. To the auxiliaries he spoke of high pay for the moment and rich spoils in the distribution of the spoil. Speaking to the Gauls, he revived in his spirit the fire of that national and natural hatred that fed against Rome. In the eyes of the ligurines it made the hope of changing its abrupt mountains through the fertile plains of Italy. He frightened the Moors and Noids with the picture of the cruel despotism with which Masinissa would overwhelm them; and addressing others he pointed to them other fears and other hopes. To the Carthaginians he spoke of the walls of the homeland, of the gods of the heathen, of the graves of his fathers, of his sons, of his relatives, of his desolate wives.

Tito Livio, XXX

For example, as Arthur Schopenhauer points out, paraphrasing Aristotle, if the interlocutor «is a supporter of a sect with which we do not agree, we can use against him the maxims of that sect as principle».

Writers consider that the ad hominem argument is a resource that is used for practical purposes, in philosophical, legal, political discussions, etc., whenever it is intended to persuade someone of something, which is which requires sharing with the audience some of the premises, even if only theoretically:

The possibilities of argumentation depend on what each one is willing to grant, of the values he recognizes, of the facts on which he points out his conformity; therefore, any argumentation is a argument ad hominem or ex concessis.

Chaim Perelman