Critical Thinking: What It Is and How to Get Better at It

What is critical thinking?

Critical thinking is judging claims by their evidence and reasoning. It is the discipline of asking “how do we know that?” before accepting something, including when the claim comes from someone you trust or confirms what you already believe.

The idea is old. Socrates is remembered for questioning people until the weak points in their beliefs appeared. In the twentieth century, the philosopher John Dewey described “reflective thinking” in How We Think (1910): active, careful consideration of a belief in light of the grounds that support it. In 1990, a panel of experts convened by the American Philosophical Association, with Peter Facione as lead investigator, produced a consensus definition known as the Delphi Report. It described critical thinking as purposeful, self-regulatory judgment, and listed the skills and dispositions involved.

A plain working definition: critical thinking is reaching conclusions you could defend to a smart, fair person who disagrees with you.

What critical thinking is not:

• It is not cynicism. Rejecting everything is as lazy as accepting everything.
• It is not winning arguments. Debating skill can be used to defend bad conclusions very well.
• It is not the same as intelligence. Smart people are often better at building reasons for what they already believe.

Why critical thinking matters

You make judgments all day based on claims you can’t check personally: news, product reviews, medical advice, a colleague’s forecast, a sales pitch. Critical thinking is the filter between those claims and your decisions.

It matters most in three places:

1. When stakes are high. A health choice, a financial decision, a hiring call. A bad filter here is expensive.
2. When the claim is one you like. Your guard goes down for conclusions that flatter you or your side. That is confirmation bias, and it is the main enemy of critical thinking.
3. When information is cheap and confident. Anyone can publish a polished claim. Confidence is not evidence.

The core critical thinking skills

The Delphi Report named six core skills. They are a good map, because each one is a different question you can ask. The full breakdown, with exercises for each, is in the guide to critical thinking skills.

Skill	The question it asks	Example
Interpretation	What exactly is being said?	“Sales grew 50%” from what base, over what period?
Analysis	What are the claim, the reasons and the assumptions?	The argument assumes last year’s customers will stay
Evaluation	How strong is the evidence and the source?	A single anecdote vs a large, controlled study
Inference	What follows, and what else could explain this?	Higher sales could be a price cut, not the new ad
Explanation	Can I state my reasoning clearly?	Writing your conclusion and the three reasons for it
Self-regulation	Where might I be wrong?	Checking whether you’d accept this evidence if it pointed the other way

Of the six, self-regulation is the one that separates critical thinkers from clever arguers. It means turning the same scrutiny on your own reasoning that you turn on others’.

The dispositions behind the skills

Skills are only half of it. The Delphi panel also stressed dispositions: the willingness to use the skills. These include curiosity, open-mindedness, fair-mindedness, and the honesty to face your own biases. A person with strong skills and weak dispositions will use logic to protect their opinions.

A practice routine for critical thinking

Critical thinking improves with deliberate practice, but it doesn’t transfer automatically. Practicing logic puzzles mostly makes you better at logic puzzles. What transfers better is a small set of questions you ask across many kinds of claims. Here is a 15-minute routine you can run a few times a week.

1. Pick one claim (2 minutes). A headline, a statement in a meeting, a post you agreed with. Pick ones you agree with at least half the time.
2. Restate it precisely (2 minutes). Write the claim in one sentence, with numbers and scope. Vague claims can’t be checked. “Remote work kills productivity” becomes “Teams that switched to remote work produced less output per person.”
3. List the support (3 minutes). What evidence is offered? Is it data, an anecdote, an authority, or just repetition?
4. Name the assumption (2 minutes). What has to be true for the evidence to support the claim? This is usually where the argument is weakest.
5. Generate one alternative explanation (3 minutes). What else could explain the same evidence? Correlation, selection effects and survivorship are frequent culprits.
6. Steelman the other side (2 minutes). Write the strongest version of the opposing view. Steelmanning is the most direct exercise for self-regulation.
7. Rate your confidence (1 minute). Not true or false: a percentage. Then note what evidence would move it.

Keep a running note of the claims and your ratings. After a month, look for patterns: which kinds of sources fooled you, which assumptions you tend to miss.

Common failures: biases and fallacies

Critical thinking fails in two main ways: errors in the judging process (cognitive biases) and errors in argument structure (logical fallacies).

Cognitive biases

Cognitive biases are predictable distortions in how you form judgments. The ones that most often defeat critical thinking:

• Confirmation bias: seeking and favoring evidence that fits what you believe.
• Halo effect: trusting a claim because of who made it.
• Bandwagon effect: believing something because many others do.
• Availability heuristic: judging how common something is by how easily examples come to mind.
• Dunning-Kruger effect: low skill in an area often comes with overestimating your performance in it.

Logical fallacies

Logical fallacies are flaws in argument structure: the conclusion doesn’t follow from the premises, even if it feels like it does. Common ones include the straw man (attacking a weaker version of the argument), ad hominem (attacking the person), false dilemma (presenting two options when there are more) and appeal to authority (treating an expert’s word as proof outside their field).

	Cognitive bias	Logical fallacy
Where the error lives	In your judgment process	In the argument’s structure
Can you see it on paper?	Usually not	Usually yes
Who commits it	Everyone, automatically	Anyone making or accepting an argument
Main defense	Process and habits	Checking premises and logic

The two feed each other. Biases make you more likely to accept a fallacy whose conclusion you like, and less likely to notice it.

Critical thinking and mental models

Mental models are the toolkit critical thinking uses. Where critical thinking asks “is this claim justified?”, a mental model gives you a specific way to check. A few that do the most work:

• First-principles thinking: break a claim down to what you know is true and rebuild from there.
• Occam’s razor: prefer the simpler explanation that fits the facts.
• Base rates: ask how common the thing is in general before judging the specific case.
• Map is not the territory: every summary, chart or statistic leaves things out. Ask what.
• Inversion: ask what would make the claim false and whether you have looked.

Critical thinking examples from everyday life

Critical thinking is easiest to see in small moments. These examples are hypothetical, but the patterns are common.

• At work. Say a colleague presents a chart showing that customers who use a new feature stay longer. A critical thinker asks whether the feature keeps customers, or whether loyal customers are simply more likely to try new features. Same data, two very different conclusions.
• With health news. Say a headline reports that a food “doubles your risk” of a disease. The useful questions: doubles from what to what? In how many people? Was it an experiment or an observation? A risk going from 1 in 10,000 to 2 in 10,000 is a very different story from 10% to 20%.
• With money. Say a friend made a lot of money on one stock and recommends it. Before acting, you would ask how many similar picks lost money, which is a question about the graveyard, not the winner.
• In an argument. Say you are sure you are right in a disagreement with your partner. Restating their view until they say “yes, that’s what I mean” often reveals that you were arguing about different things.

In each case, the move is the same: slow down long enough to ask what is really being claimed and what else could explain it.

Critical thinking in decisions

Critical thinking is most valuable when it feeds a decision. Evaluating claims is the input; choosing well is the output. The decision-making guide shows where it fits: the Stress-test step of the Mentarium Decision Loop is critical thinking aimed at your own favorite option, using the Bias Radar to check the seven biases most likely to distort that kind of choice.

The Mentarium take

The usual pitch for critical thinking is about defending yourself from other people’s bad arguments: misinformation, sales tactics, sloppy reasoning. That matters, but it is the easier half. Spotting a weak argument for a conclusion you dislike takes almost no skill.

The real test of critical thinking is the claim you want to be true. A business idea you are excited about, a study that supports your diet, a forecast that justifies what you already planned. That is where self-regulation earns its place in the list, and where most smart people fall down.

So our practical advice: in the routine above, deliberately pick claims you agree with at least half the time. If your critical thinking only ever finds flaws in the other side, it isn’t critical thinking yet. It is advocacy with good manners.