Module 1: Thinking About Thinking

What Critical Thinking Really Is

Every day at work you are asked to believe things, decide things and solve things. A supplier says their product will cut costs. A colleague says sales fell because of the new competitor. A news story says a certain investment is guaranteed to double your money. Critical thinking is the skill of examining claims and problems carefully before you accept them or act on them. It is one of the most valuable skills in any career, because good decisions depend on it.

A working definition

Critical thinking is the disciplined process of analysing information, questioning assumptions, weighing evidence and reasoning logically to reach well-founded conclusions and decisions. It is not about being negative or criticising everything. The word "critical" here means careful judgement, not fault-finding.

A critical thinker:

• Asks clarifying questions before reaching conclusions.
• Looks for evidence and judges its quality.
• Considers alternative explanations.
• Notices their own assumptions and biases.
• Changes their mind when good evidence requires it.
• Communicates reasoning clearly so others can check it.

Fast and slow thinking

The psychologist Daniel Kahneman popularised a useful distinction between two modes of thinking, often called System 1 and System 2. System 1 is fast, automatic and intuitive: recognising a friend's face or reacting to a sudden noise. System 2 is slow, deliberate and effortful: working through a budget or comparing two job offers.

System 1 is essential; we could not get through a day without it. But it relies on shortcuts that can lead us astray, especially in unfamiliar, complex or high-stakes situations. Critical thinking is largely about knowing when to slow down and engage System 2.

Core questions of critical thinking

When facing a claim, a decision or a problem, these questions will serve you well:

1. What exactly is being claimed or asked? Clarify vague terms.
2. What is the evidence? Where does it come from, and how reliable is it?
3. What assumptions are being made? Are they reasonable?
4. What are the alternative explanations?
5. What are the implications? If this is true, what follows?
6. What is missing? What information would change the conclusion?

A worked example

Mwangi manages a chain of four hardware stores around Kiambu. His operations manager reports: "Sales dropped this quarter because the new competitor opened in Ruiru. We need to cut prices across all stores."

Instead of accepting this immediately, Mwangi applies the core questions:

• Claim: sales dropped because of the competitor, so prices should be cut everywhere.
• Evidence: he checks the data. Sales dropped at all four stores, including two that are far from Ruiru.
• Assumption: that the competitor is the main cause. But stores far away also fell.
• Alternatives: a seasonal slowdown in construction, stock shortages, or a general fall in customer spending.
• Missing information: sales by product category and stock-out records.

The category data shows the drop was mainly in cement and roofing sheets, which had been out of stock for several weeks due to a supplier problem. Cutting prices across all stores would have reduced margins without fixing the real issue. Mwangi addresses the supplier problem instead.

Why it is a skill, not a trait

Critical thinking is not something you either have or do not have. It is a set of habits and tools you can learn and practise. The lessons that follow give you those tools: spotting biases, testing assumptions, judging evidence, defining problems, analysing causes and evaluating options.

Common mistakes to avoid

• Confusing criticism with critical thinking. Rejecting every idea is as lazy as accepting every idea.
• Thinking slowly about everything. Save deliberate analysis for decisions that matter.
• Accepting a confident explanation because it sounds right. Confidence is not evidence.
• Applying critical thinking only to others' ideas. Your own conclusions need the same scrutiny.

Critical thinking is a habit of asking good questions before reaching conclusions. The rest of this course shows you how to ask them well.