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Evaluating arguments and recognize valid reasoning is a key skill in critical thinking—and once you master it, you’ll be able to spot weak arguments and build stronger ones of your own.
In this lesson, you’ll learn how to recognize common logical fallacies—the sneaky errors in reasoning that can make an argument seem stronger than it really is. These fallacies show up everywhere: in ads, debates, social media, and even serious writing.
On the AICE Thinking Skills Paper 2 exam, you’ll be asked to:
Identify which fallacy is being used in a passage, or
Find an example of a specific fallacy within a text.
You’ll also need to explain how the fallacy weakens the argument—because spotting the flaw is just the first step. Understanding its impact is what shows real critical thinking.
Memorizing the names and types of fallacies is key to answering Question #4 on Paper 2!
Step 1: Spotting Flaws in Reasoning
When you evaluate an argument, your goal is to find any flaws or weaknesses in the reasoning. Ask yourself:
Step 1: Spotting Flaws in Reasoning
When you evaluate an argument, your goal is to find any flaws or weaknesses in the reasoning. Ask yourself:
How big is the flaw?
Does it affect the entire argument or just one part?How serious is it?
Does it completely destroy the claim, or just make it less convincing?Is anything still salvageable?
Even if part of the argument is flawed, could a weaker version still make sense?
Step 2: Understanding Validity
Step 2: Understanding Validity
Validity is all about the structure of an argument—not whether the statements are true, but whether the reasoning is logically sound.
A valid argument means: If the reasons are true, then the conclusion must also be true.
Think of it like math or coding: the logic has to follow a clear pattern.
Step 3: Using Letters to Represent Logic
Step 3: Using Letters to Represent Logic
To focus on structure, we often use letters like p and q:
If p, then q.
p is true.
Therefore, q is true.
This is called Modus Ponens—a valid form of reasoning.
Examples of Valid Arguments:
Examples of Valid Arguments:
If Emma is a student at Sunny Coast College, she can borrow books.
Emma is a student.
So, she can borrow books.
If a compound is acidic, it turns litmus paper red.
This compound is acidic.
So, it turns the paper red.
Even if the content is silly, the structure can still be valid:
If someone is 3 meters tall, they can touch the moon.
My friend is 3 meters tall.
So, they can touch the moon.
(Valid structure, but obviously false in reality!)
Step 4: The Negative Version
Step 4: The Negative Version
Another valid structure flips the logic:
If p, then q.
q is not true.
Therefore, p is not true.
Examples:
Examples:
If Emma is a student, she can borrow books.
She can’t borrow books.
So, she’s not a student.
If a compound is acidic, it turns litmus paper red.
It doesn’t turn red.
So, it’s not acidic.
Step 5: Watch Out for Invalid Structures
Step 5: Watch Out for Invalid Structures
Some arguments look logical but are actually flawed. These are invalid:
If p, then q.
q is true.
So, p is true. ❌If p, then q.
p is false.
So, q is false. ❌
Examples of Invalid Arguments:
Examples of Invalid Arguments:
If Sofia is a student, she can borrow books.
She can borrow books.
So, she must be a student
(Maybe she’s a teacher or a guest member!)
If Petra is a student, she can borrow books.
She’s not a student.
So, she can’t borrow books.
(Again, she might qualify in another way.)
Necessary and Sufficient Conditions
A necessary condition is something that must be true or must happen for something else to be true or happen.
Example:
Example:
To get into a movie theater, you must have a ticket.
Having a ticket is necessary to enter.
But just having a ticket doesn’t guarantee you’ll see the movie—you might be late, or the theater might be closed. So it’s necessary, but not always enough.
A sufficient condition is something that, if it happens, guarantees that something else will happen.
Think of it like a guarantee.
Example:
Example:
If you score 100% on the test, you will pass the course.
Scoring 100% is sufficient to pass.
But it’s not necessary—you could also pass with 85%. So scoring 100% is more than enough, but not the only way.
There are two rules a good argument must follow are:
The reasons should be true, as far as it is possible to judge.
The conclusion must follow recognizably from the reasons, meaning that if the reasons are all true, the conclusion cannot be false.
An argument that passes both these rules is said to be sound, and if an argument fails one or both then it is unsound. Another word to describe an unsound argument is to say that it is flawed. A flaw is a fault. An argument can have true premises and a true conclusion and still be flawed. However, if the conclusion is known to be true there is no real need for an argument.
Rash Generalization - A conclusion based on too little evidence.
Example: Three people fell into the ice last winter when they were walking across the lake. No one should ever think of walking on frozen lakes.
Sweeping Generalization - A rule applied too broadly, without allowing for exceptions.
Example: A law that infringes the freedom of the individual is never acceptable.
Equivocation - Using a word in two different ways within the same argument.
Example: The average family has 2.4 children. Since the Bell family is about as average as you can get, the Bells must have either two or three children.
Conflation - Mixing up two ideas or treating them as the same when they’re not.
Example: You are wrong to criticise people who lack ambition. Take your own father who chose a career that would never bring him wealth or status. He didn’t want those things and didn’t value them. Surely you don’t despise him
False dichotomy (restricting the options) - Presenting only two choices when more exist.
Example: The Treasury Minister’s plan is nonsense. She’s a monster who voted for her own pay raise last year
Ad Hominem (Personal Attack) - Attacking the person instead of their argument.
Example: The Treasury Minister’s plan is nonsense. She’s a monster who voted for her own pay raise last year.
Tu quoque (counter-attack) - Responding to criticism with unrelated accusations.
Example: Tom: “It’s wrong to jump the queue for hospital treatment.”
Joe: “You sent your kids to private school!”
Straw Man - Misrepresenting someone’s argument to make it easier to attack.
Example: Jay: “Dumping trash on the floor isn’t art.”
Kay: “That’s nonsense—art doesn’t have to be pretty.”
Circular Reasoning - The conclusion is just a restatement of the premise.
Example: Exams are essential because they motivate students. Without exams, students wouldn’t be motivated. So exams are essential.
Begging the Question - Assuming the very thing you’re trying to prove.
Example: Killing is wrong, so the death penalty is immoral.
Slippery Slope - Claiming a small step will lead to a chain of extreme consequences.
Example: Chewing gum leads to litter, which leads to graffiti, which leads to gangs and violence.
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