Syllogism is a form of deductive reasoning where you arrive at a specific conclusion by examining two other premises or ideas. Syllogism derives from the Greek word syllogismos, meaning conclusion or inference.
Some syllogisms contain three components:
For Example: All roses are flowers (major premise). This is a rose (minor premise). Therefore, I am holding a flower (conclusion).
The type of syllogism that typically contains these three components is categorical syllogism. However, there are two other major kinds of syllogism. We'll discuss each one here, plus enthymemes and syllogistic fallacy.
As we know, our first example about roses was a categorical syllogism. Categorical syllogisms follow an "If A is part of C, then B is part of C" logic.
Let's look at some more examples.
Conditional syllogisms follow an "If A is true, then B is true" pattern of logic. They're often referred to as hypothetical syllogisms because the arguments aren't always valid. Sometimes they're merely an accepted truth.
Disjunctive syllogisms follow a "Since A is true, B must be false" premise. They don't state if a major or minor premise is correct. But it's understood that one of them is correct.
Major Premise: This cake is either red velvet or chocolate.
Minor Premise: It's not chocolate.
Conclusion: This cake is red velvet.
Major Premise: On the TV show Outlander, Claire's husband is either dead or alive.
Minor Premise: He's not alive.
Conclusion: Claire's husband is dead.
An enthymeme is not one of the major types of syllogism but is what's known as rhetorical syllogism. These are often used in persuasive speeches and arguments.
Generally, the speaker will omit a major or minor premise, assuming it's already accepted by the audience.
In an enthymeme, one premise remains implied. In the examples above, being familiar with someone or something implies an understanding of them.
Some syllogisms contain false presumptions. When you start assuming one of the major or minor premises to be true, even though they're not based in fact - as with disjunctive syllogisms and enthymemes - you run the risk of making a false presumption.
Of course, not every black bird is a crow and not all of Ireland is beautiful. When preparing a speech or writing a paper, we must always make sure we're not making any sweeping generalizations that will cause people to make false presumptions.
There are six known rules of syllogism. However, they mainly apply to categorical syllogism, since that is the only category that requires three components: major premise, minor premise, conclusion. Here are six rules that will ensure you're making a strong and accurate argument.
Syllogisms make for colorful literary devices. They explain situations indirectly, affording readers the opportunity to practice reasoning and deduction skills. Shakespeare was a master of many things, including syllogism. Here is an example of a syllogism fallacy in The Merchant of Venice:
Portia was a woman desired by many men. It was arranged she would marry the man who could correctly guess which of three caskets contained her portrait.
One casket was inscribed with, "Who chooseth me shall gain what many men desire." One man concluded that, since many men desired Portia, her portrait must be in that casket.
He was wrong. His assumption falls under the category of syllogistic fallacy. One cannot deduce that, since this casket contains what men desire, it's automatically the portrait. Men also desire fortune and power, for example. There wasn't enough evidence to leap from premise to conclusion here.
Socrates set up one of the most famous, and easily understand, examples of syllogism in philosophy. He clearly followed the rule of three components.
All men are mortal. Socrates is a man. Therefore, I am mortal.
This draws a clear picture of how one statement, when known to be universally true, should point perfectly to another clear claim, thus drawing an accurate conclusion.
Keep syllogisms in mind when viewing advertisements. Many leaps are made in advertising, skipping either a major or minor premise:
Women love men who drive Lincoln MKZs.
Get ready for an enthymeme or syllogism fallacy. A blanket statement such as this skips one of the two required premises. Every time a woman likes a man, it can't be assumed he drives a Lincoln MKZ.
Understanding syllogisms will help you create masterful persuasive speeches and essays. They create a formula for you to abide by, in order to ensure your main point is flawless.
Syllogisms also allow you to test your theories according to syllogistic fallacies. When examining your main argument or point for discussion, be sure you haven't made any presumptions that your audience might disagree with.
Maybe some women won't like MKZs. Perhaps they prefer a good 'ol fashioned Mustang! Just keep your eyes and ears open while you allow syllogisms to drive your point home with clarity and truth.