Aristotle’s Syllogism & Enthymeme: Part 1

Today, imagining a world without logic and figurative language seems impossible, but ancient Greeks and Romans actually invented the ways of thinking we regard as self-evident. They crafted ways to communicate abstract concepts and persuade others about them through their studies of rhetoric. Aristotle, a Greek rhetorician, defined rhetoric as finding the best possible means of persuasion in the particular case. Aristotle’s teachings about rhetoric included definitions and explanations for the terms “syllogism” and “enthymeme,” linguistic devices that convey logos, pathos, and ethos. By examining the term “syllogism” and showing how it branches to the concept “enthymeme,” we will see why enthymemes are more useful to rhetoricians, whereas syllogisms are more useful to scientists.


Syllogisms can be explained through taxonomy (the science of distinguishing and categorizing living organisms). A scientist knows that a chihuahua is a canine because the canine genus includes the domestic dog species, and that species includes the chihuahua subspecies. Aristotle, a field biologist prior to a rhetorician, was trained in taxonomy. When one creates a syllogism, one defines a broad category (genus), then one defines another category that falls within the broad category (species). Whatever belongs to the smaller category must also belong to the broad category. The classic example of syllogism reads, “All men are mortal. Socrates is a man. Therefore, Socrates is a mortal.” First, the syllogism defines a broad category, mortals, which encompasses a smaller category, men. Secondly, it claims that the smaller category, men, includes an even smaller category, Socrates. Thirdly, the syllogism concludes that the smallest category, Socrates, must belong to the broadest category, mortals. In other words, if A includes B and B includes C, A must include C. The definition of the broadest category is called the major premise, and the one for the smaller category is called the minor premise, while the final connection between the premises is called the conclusion.     


An enthymeme functions like a syllogism, but its terms for distinction and categorization differ from syllogism. Aristotle called those terms “topics.” Syllogisms use the topic definition/implication. In the Socrates syllogism example above, the major and minor premises are scientific facts–it is irrefutable that men are mortals and that Socrates was a man. An enthymeme varies from a syllogism because enthymemes are based in probabilities rather than facts. Rather than the topic being definition/implication, it may be cause and effect, comparisons, relationship between part and whole, etc. Types of probability detailed by Aristotle include fallible/infallible signs, examples, and generally true statements. For instance, the statement “I need to let the dog out because he’s whining” is an enthymeme if the owner assumes that the dog whines when it needs to defecate. The major premise, minor premise, and conclusion are: “The dog whines when it needs to use the bathroom. The dog is whining. Therefore, the dog needs to use the bathroom.” In that instance, as with the next one, every part of the enthymeme is not stated originally; rather, the parts of the enthymeme are broken down afterwards to reveal the line of reasoning behind them. Each part is usually not said because, according to Aristotle, “if one of these elements is something notorious, it need not even be stated, as the hearer himself supplies it.” Here’s another example of an enthymeme with a generally true statement instead of a sign: “He ate breakfast this morning, but since it’s almost 12 pm, we should send him out for lunch soon.” It’s generally true that humans need to eat food every few hours. In this scenario, “humans need to eat every few hours” is the major premise, “he hasn’t eaten in a few hours” is the minor premise, and “therefore, he will need to eat soon” is the conclusion. While syllogisms logically link facts together, enthymemes rely heavily on assumption, experience, and observation.

Stay tuned for the other half of the essay!

Works Cited

Golden, James, et al. The Rhetoric of Western Thought. 10th ed., Kendall Hunt Publishing Company, 2011.


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