Syllogism is an important topic for the section of the paper testing a candidate’s reasoning ability. A Syllogism is a form of reasoning conceptualised by Aristotle wherein you arrive at a specific conclusion by examining two other premises or ideas. In essence, a syllogism is a type of deductive reasoning where the answer is derived by deducting improbable options to arrive at the correct answer. Syllogism derives its name from the Greek word syllogismos, which means deduction or inference.
All syllogistic arguments have 3 parts.
Syllogistic statements/arguments are generally provided in a three-line format, as depicted below:
All cats are wearing a bell
Lily is a cat
Therefore, Lily is wearing a bell.
Categorical syllogisms follow a rule wherein "if A is party to C, then B is party to C”. As we can see, the first example with cats falls under this category.
Let's look at another example of a categorical syllogism.
All horses have 4 legs. I have a horse. My horse has 4 legs.
Major Premise: All horses have legs
Minor Premise: I have a horse.
Conclusion: My horse has 4 legs.
Conditional syllogisms follow an "If idea A is true, then idea B is true is true as well" logic. These conditional syllogisms may also be referred to as hypothetical syllogisms. This is because the arguments presented aren't always valid. They are simply accepted because idea B has a direct relation with the idea and is therefore assumed to be true.
Study the following examples:
If Rahul likes biscuits, he will like Oreos.
Major premise: Rahul likes biscuits
Minor premise: Oreos are biscuits
Conclusion: Rahul will like Oreos.
Rahul may or may not like Oreos. But since it is mentioned that Rahul likes biscuits it can be assumed that Rahul likes Oreos as well.
If Sakina likes to travel, she must want to visit Morocco.
Major premise: Sakina likes to travel.
Minor premise: Sakina will like to travel anywhere.
Conclusion: Sakina will travel to Morocco.
Disjunctive syllogisms follow an “either A or B is true, if it's A, B is false" format. It contains only 2 premises and the possibility of both statements A and B being correct is mutually exclusive. The statements themselves do not explicitly say if either statement is correct or not. But it's understood that one of them is correct.
The ink is either blue or black
The ink is not blue
The ink is black
Some syllogisms may contain false assumptions that are not based on facts. Here, the major premise is assumed to be true from which the other two premises are drawn. Hence, we run the risk of making false assumptions.
All Dell laptops are black.
My laptop is black.
Therefore, mine is a Dell laptop.
Major Premise: All Dell laptops are black.
Minor Premise: My laptop is black.
Conclusion: My laptop is also a Dell laptop.
All German people can sing beautifully. My neighbour is German. Therefore, he must sing beautifully.
Major Premise: All Germans sing beautifully.
Minor Premise: My neighbour is German.
Conclusion: My neighbour sings beautifully.
Another type of syllogism which is infrequently tested is an enthymeme. It uses rhetorical arguments and persuasion to make an argument. This is why it is also called a rhetorical syllogism. Here, the minor premise is generally omitted assuming that the audience is also convinced of the same.
Her dress must be so expensive, I know the designer.
Major Premise: Her dress must be expensive.
Minor Premise: I know the designer.
Her new purse can't be ugly. It's a Louis Vuitton.
Major Premise: Her new accessory can't be ugly.
Minor Premise: It's made by famous designer Louis Vuitton.
In an enthymeme, one premise remains implied. In the examples above, we see that the notion of familiarity with someone or something implies an understanding of them and thereby swaying opinion about the same.
Rules of Syllogism
Syllogisms follow 6 basic rules. However, these rules mainly apply to categorical syllogism, as it is the only king of syllogism that mandatorily requires three components as shown above. Let us understand these 6 rules given below to ensure that the candidate devises an error-free argument.
Named after its designer, John Venn, Venn Diagrams have illustrated circles that intersect at one common point. For syllogisms, these Venn diagrams help us to confirm the accuracy of the statements presented. These diagrams help us especially when complex syllogisms need to be solved. Let us illustrate with a simple example.