How to overcome flawed thinking in GMAT Critical Reasoning?

Critical Reasoning is a skill that you cannot develop in a couple of days. But GMAT Critical reasoning can be mastered if you understand some of the common pitfalls in our logical deduction. The most common mistakes are made in Syllogism.



What is Syllogism?

A Syllogism is a type of argument where you have a conclusion based on one or more premises. Let’s look at an example

Premise 1: All roses are flowers

Premise 2: Some flowers have thorn

Conclusion: Therefore Some roses have thorn

Most GMAT test taker would agree with the conclusion or naturally make such conclusions when they are presented with similar critical reasoning questions. The CONCLUSION is wrong! We are intuitive creatures. Even when our logical mind asks us to think before making any conclusion, the lazy intuitive mind will force us to make the obvious wrong conclusion. Another factor that contributes to the wrong conclusion is the use of our knowledge about roses (that it has thorns) to make the conclusion.

Remember, GMAT Critical reasoning requires you to make conclusion purely based on the premises provided.

How to overcome flaws in logical thinking for GMAT Critical Reasoning Questions?

The trick here is to identify the terms used in the Syllogism

There are three terms: Major Term, Minor Term and Middle Term

Premise having Major Term is the Major Premise

Premise having Minor Term is the Minor Premise

How to identify Major and Minor Terms?

The subject of the conclusion is the Minor Term

Conclusion: Therefore Some roses have thorn

Subject = Roses = Minor Term

Predicate Term or category/concept used to describe the subject is the Major Term

Predicate Term = Thorn = Major Term

Where does the minor term (roses) appear?

Premise 1: All roses are flowers
Premise 1 = Minor Premise

Where does the major term (Thorn) appear?

Premise 2: Some flowers have thorn
Premise 2 = Major Premise

Which term does not feature in the conclusion but plays an important role in the logical deduction?

Flowers
Flowers = Middle Term

What is the use of understanding types of terms and premises?

By familiarizing yourself with the terms and premises, it would become much easier to solve GMAT Critical Reasoning questions.

PROVE IT!

Here we go:

Premise 1: All roses are flowers
Premise 2: Some flowers have thorn
Conclusion: Therefore Some roses have thorn

Step by Step Instructions to Solve GMAT Critical Reasoning Tricky Questions

1) Identify absolute premise (Arguments with “All”, “None”)

Absolute Premise: Premise 1

2) Represent the terms as alphabets

Roses = Minor Term = C
Flowers = Middle Term = B
Thorn = Major Term = A

All C in B
Some B in A
Therefore Some C in A

3) Draw Venn Diagrams starting with the absolute premise first.

Absolute Premise = All C in B             

                                                              

4) Next Premise

Some B in A

5)  Two ways to present Some B in A

Case 1: Some B intersecting A without intersecting C


Case 2: Some B in A such that A and C intersects




Conclusion: Some C in A

Not necessarily true

Conclusion is wrong. The conclusion should be true for all conditions. In this case it is false for Case 1

It is tough to go through so many steps to solve a simple GMAT CR Question in a minute.

True. But once you practice with Venn diagrams, your knowledge about a subject or intuitive traps will not affect your ability to make correct conclusions.