What is the Rhetorical Syllogism?

The enthymeme is also known as the rhetorical syllogism. In explaining this device Aristotle references his Rhetoric, Prior Analytics, and Topics as well as other of his books. While Aristotle did not favor using persuasion in an unethical fashion, it became necessary to explain the enthymeme in order to refute other less ethical enthymemes that were used by some sophists of the time. To understand the enthymeme or rhetorical syllogism one must first understand a syllogism.

The Syllogism – Validity and Soundness

A normal syllogism has 2 premises and a conclusion. For example one could say the following:

All Men are Mortal (premise)

Socrates is a Man (premise)

Therefore Socrates is a Mortal (conclusion)

This is a valid and sound syllogism. Validity refers to when the conclusion follows from the premises, and a sound argument is a valid argument plus the premises are true. In the enthymeme one line or more in the syllogism is implied, and therefore not explicitly stated. For example in the following truncated syllogism, the premise “Socrates is a Man” is implied, and still the premises and the conclusion are clear.

All Men are Mortal (premise)

Therefore Socrates is Mortal (conclusion)

But the enthymeme is not simply based on syllogistic logic, although syllogistic logic is a very important part of it. The enthymeme also tugs at the emotions. Lastly it appeals to ones sense of what is right or wrong (e.g., ethics) How is a syllogism able to accomplish this?

The Persuasive Nature of the Enthymeme

The enthymeme is a popular technique of demogogues. People are persuaded to accept as true false beliefs against their will. While such a thing may not seem possible, when one examines the enthymeme one can see why this is so. Central to the enthymeme is understandinglogospathos, and ethos (e.g., logic, emotion and ethics).

First of all the logical aspect is clear. The syllogism is a tried and true method in logic, and is used in most of Aristotle’s logical systems. But this is not only what makes the enthymeme so treacherous.

One’s emotions are engaged. This is so first of all because with the enthymeme that is used, the auditor (e.g., the listener) agrees with the premises, agrees with the logical structure, and therefore is compelled to believe that the enthymeme, or truncated syllogism, is in fact valid and sound. Most importantly the auditor themselves supply the missing premise or conclusion. This makes their belief integral in the enthymeme. This fact of agreement with the enthymeme elicits an emotional response, a satisfaction that one’s beliefs are validated by logic. Also the enthymeme can also elicit an emotional response when being compelled to accept false premises based on flawed information which may be favorable to the auditor.

Finally this affirmation, this confirmation of the auditor to this unsound truncated syllogism convinces the auditor to agree with the rhetor (e.g., the rhetorician) about issues that concern society. The auditor is convinced that this truncated syllogism appeals to them directly and is enshrined in logic, and the auditor can then go so far as to believe that the false agreement with this syllogism goes on to validate oneself and their standing in the community (e.g., ethos).

An Example of an Enthymeme

Take the following example:

Former President George H. W Bush offered the following enthymeme when opposing the Civil Rights Bill of 1991. He explicitly states the observation only.

Observation: The bill will promote the use of quotas in the workplace.

Generalization: Quotas give unearned opportunities to minorities.

Inference: White’s opportunities will unfairly be given to minorities if the bill passes.

His audience was his fellow Republicans composed disproportionately of whites compared to the Democratic Party. Yet this enthymeme could have a very different meaning if given to an audience composed of minorities.

For example:

Observation: The bill will promote the use of quotas in the workplace.

Generalization: Quotas insure that earned opportunities will be given to minorities.

Inference: Minorities will be treated fairly in the hiring process.

Is the Enthymeme Ethical?

Enthymemes are persuasive independent of the facts of the matter. But it is only ethical when the truncated premise or conclusion is used with the full knowledge of the auditor, that is where the meaning of the missing premise or conclusion is clearly understood. The facts in the world, determine if the enthymeme not only appears to be ethical, but in fact is ethical.

A side note in dealing with enthymemes in general; by identifying the erroneous implied premises one can in fact refute unethical enthymemes by constructing your own. So have at it!


Aden, Roger C. The Enthymeme as Postmodern Argument Form: Condensed, Mediated Argument Then and Now. Argumentation and Advocacy 31, no. 2 (Fall 1994): 59.

Barnes, Jonathan Ed. The Complete Works of Aristotle: The Revised Oxford Translation. Bollingen Series LXXI, Princeton University Press 1995

Frame, Doug., The Logical Nature of Aristotle’s Enthymeme. Masters Thesis 1998

Informal Logic and the Ad Hominem Fallacy

There are many types of logical fallacies one discovers when talking about critical thinking. Some rely on formal logic such as the enthymeme or rhetorical syllogism, and others rely on what are called informal fallacies. These are fallacies not based directly on logic but rather often deal with emotions or what could be referred to as sleights of hand. One informal fallacy that has a lot of variation is called the Ad Hominem fallacy which mean literally “against the man.” Here are the main variations of the Ad Hominem fallacies.

 Ad Hominem Abusive

This fallacy is the best known of the Ad Hominem fallacies. This informal logical fallacy attacks the person rather than an individual’s personal position. An example of the Ad Hominem fallacy is the following: Henry cannot have any good ideas about financial planning because Henry is a drunk. The argument tells one nothing useful about whether Henry is a competent financial planner or not but rather attacks him personally to discredit him.

Ad Hominem Circumstantial.

This too is an attack on ones character but is less direct than the Ad Hominem abusive. An example of this might be “union support raising the workers` wages will most likely increase the pay of the labor union representatives.” The implication is that the union representative efforts to increase labor pay is only because the union representative wants to pad their own pockets.

Ad Hominem “Tu Quoque” or “you too” fallacy.

One might argue for example that one shouldn’t steal. Some may cheat on their taxes. A father might tell his son that it is wrong to steal. His son might say back to him that “you steal on your taxes so who are you to tell me about stealing?” The assertion by the son is that since dad does it it is ok for him to do it. Yet this ignores the fact that stealing is wrong in any circumstances.

Ad Hominem Inconsistency

An example might be when a politician claims that there should be no new taxes. Yet later in ones career that same person might vote to raise taxes. Such a person might be accused of being unreliable and even not worthy of trust. This ignores the fact that the financial circumstances of the country may have changed and therefore at this time raising taxes may have been prudent and warranted. Yet with this fallacy the implication can be that the politician is untrustworthy or ever dishonest.

Ad Hominem Poisoning the Well.

Someone might claim that such and such homosexual “in this case doesn’t have AIDS”. The insinuation here is that being homosexual (especially this homosexual) is associated with AIDS. While the claim does not directly say this person has ever been exposed to AIDS, an association is drawn between this individual and AIDS. This can be used to further attack ones character.

Positive Ad Hominem Fallacy.

Just as someone’s integrity can be attacked by the Ad Hominem, the Ad Hominem can (theoretically) also be used to establish virtue. For example one might say that so and so goes to church every Sunday and therefore it is unlikely that the person falsified accounting entries at the company where the accused is the controller. But anyone is capable of falsifying accounting entries, even those that go to church.


  • Copi, Irving, and Cohen, Carl. Introduction to Logic. New Jersey: Prentice Hall, 1998.
  • Hurley, Patrick. A Concise introduction to Logic. Belmont: Wadsworth 2000.