What Counts as Evidence?
Tools for Thinking Clearly
Evidence, anecdote, and intuition each play a role in how we form beliefs — but they are not interchangeable. This topic explains what distinguishes strong evidence from weak, why the distinction matters, and how different types of evidence should be weighted when evaluating a claim.
Learning Material
4 pagesThe Question Behind Every Claim
Every claim you encounter — in a news article, a friend's argument, a social media post, a government announcement — carries an implicit promise: trust me, this is true. The question that separates careful thinking from passive reception is simple: what is this claim actually based on?
This is not a question about distrust. It is a question about calibration. Carl Sagan, the astronomer and science communicator, put it plainly: extraordinary claims require extraordinary evidence (Sagan, 1995, p. 62). The corollary is equally important — ordinary claims also require some evidence, even if less of it.
In everyday life we routinely treat different kinds of information as if they were interchangeable: a personal story, a statistic, a scientific paper, a feeling of certainty. They are not interchangeable. Each carries a different amount of evidential weight, and understanding the difference is the foundation of clearer thinking.
Why this matters beyond the classroom
The stakes are practical. People make decisions about health, money, politics, and relationships based on information of wildly varying quality. When a claim lacks supporting evidence but is presented confidently — by a charismatic speaker, a trusted source, or through sheer repetition — it can be adopted as fact without scrutiny.
Psychologist Daniel Kahneman has documented extensively how human cognition is not naturally calibrated to weigh evidence carefully. Our 'System 1' thinking — fast, intuitive, emotionally resonant — is prone to accepting claims that feel right without engaging the slower, more analytical 'System 2' thinking that would actually evaluate the underlying support (Kahneman, 2011, pp. 19–30). Recognising that this is a universal feature of human cognition, not a personal failing, is the first step.
What this topic covers
This topic examines what evidence actually is, how different types of evidence differ in strength, and how evidence can be selectively presented to mislead without technically lying. By the end, you will have a working framework for asking better questions when any claim is put in front of you.