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Evidence, Certainty & Truth
Three foundational concepts that underpin every knowledge claim. Understanding how they interact is essential for the TOK essay and exhibition.
Evidence
The grounds on which a knowledge claim is made. What counts as evidence varies dramatically across AOKs and cultures.
Certainty
The degree of confidence we can have in a knowledge claim. Rarely absolute — the question is what level of certainty is appropriate in each context.
Truth
What makes a knowledge claim correct? Correspondence, coherence, pragmatic utility — different theories of truth give different answers.
The 12 TOK Concepts: An Overview
The IB TOK curriculum identifies 12 key concepts that recur across Areas of Knowledge and Themes. These are not abstract philosophical categories to be memorised — they are analytical tools to be applied. A TOK student who can use these concepts precisely and in context will produce far stronger essays and exhibitions than one who merely lists them. The 12 concepts are: Evidence, Certainty, Truth, Interpretation, Power, Justification, Explanation, Objectivity, Perspective, Culture, Values, and Responsibility.
This page covers the first three: Evidence, Certainty, and Truth — the concepts most directly concerned with the epistemic status of knowledge claims.
Concept Deep Dives
Evidence
Evidence is any information or experience that bears on the truth or probability of a knowledge claim. But “what counts as evidence” is one of TOK’s richest questions. In Natural Sciences, evidence requires reproducibility and experimental control. In History, evidence consists of primary sources whose authenticity must be verified and whose bias must be assessed. In Mathematics, the notion of evidence barely applies — proofs provide certainty without empirical evidence. In the Arts, evidence for interpretation is a matter of ongoing debate: does the text, the author’s intention, or the reader’s response constitute evidence for meaning?
Certainty
Certainty is rarely binary in TOK — the interesting question is almost always about degree. Mathematical certainty (deductive proof from axioms) is the strongest form: a proven theorem is true necessarily, not merely very probably. Scientific certainty is probabilistic — we speak of theories being supported by evidence, not proven. Historical certainty is even more constrained: we can establish that certain events occurred with high confidence, but explanations and interpretations remain contested. For the TOK student, the key question is: what level of certainty is appropriate to this AOK, and what happens when we demand a level of certainty that the AOK cannot provide?
Truth
Three major theories of truth appear in TOK contexts. The correspondence theory holds that a claim is true if and only if it accurately describes a mind-independent reality. The coherence theory holds that truth is a matter of fitting into a consistent system of beliefs. The pragmatic theory holds that a claim is true if believing it is useful for action. Each theory has different implications for different AOKs: correspondence theory fits Natural Science well; coherence theory fits Mathematics; pragmatic theory fits practical knowledge domains. The question of which theory applies — and whether the same theory must apply across all AOKs — is central to many TOK essays.
Applying These Concepts in Essays
The most powerful essays don't just define these concepts — they show how their meaning shifts across AOKs. The concept of “evidence” means something fundamentally different in a criminal court versus a physics laboratory versus a historical archive. Tracing this variation is exactly what the TOK essay asks you to do.
A key move: identify moments where the same concept produces different conclusions in different AOKs, and use this variation to illuminate the title. If the title asks about certainty, showing that mathematical certainty (necessary truth) is structurally different from scientific certainty (probabilistic confirmation) and from historical certainty (best explanation from incomplete sources) gives you three rich body paragraphs with genuine intellectual depth.
Treating truth as a simple binary. Many students write as though claims are simply “true or false” — but TOK asks you to examine what makes something true, how we know when a claim is true, and whether “truth” means the same thing across different domains. An essay that engages with these meta-questions about truth will score significantly higher than one that assumes truth is self-evident.
- I can explain what counts as evidence in two different AOKs and why they differ
- I understand the difference between mathematical certainty and scientific certainty
- I can describe the three main theories of truth and give an example of each
- I can use these concepts to deepen an argument rather than just define them
- I have a specific essay-ready example that uses at least two of these concepts together