This fully scripted 60-minute IB DP Theory of Knowledge (TOK) lesson explores what counts as evidence, how standards of proof change across different domains, and who gets to decide when evidence is strong enough. It is designed around the core TOK question of whether evidence is neutral, or whether its value depends on the context, the claim, and the knower evaluating it.

The lesson begins with a short hook in which students respond to three different claims and reflect on why they demand different levels of proof in each case. It then introduces four broad domains: law, science, history, and everyday life. Students compare how each domain treats evidence and why the burden of proof changes depending on the stakes and the type of knowledge claim being made.

The main classroom task is Activity 1: The Same Envelope. Each group receives the same evidence pack about a possible food poisoning case, but each group is given a different interpreter role. These include an environmental health officer, epidemiologist, barrister, journalist, historian, and potential customer. Students apply different standards to the same five pieces of evidence and compare how legitimate but different conclusions can emerge from identical material.

The second task is Activity 2: The Evidence Tribunal. Students work through six contested cases linked to law, science, history, journalism, and everyday reasoning. These include eyewitness testimony, failed replication in psychology, a missing historical archive, lived experience testimony, an industry-funded study, and a verified photograph in the age of deepfakes. Students decide whether each claim should be accepted, treated as probable, disputed, or rejected based on the relevant domain standard.

The resource includes the full teacher walkthrough and a separate activity sheet with the evidence pack, interpreter cards, and tribunal cards. It also includes TOK knowledge questions, an exit ticket, and links to ideas such as falsifiability, reproducibility, testimonial injustice, and the burden of proof.

This resource is useful for TOK lessons on evidence, proof, justification, the knower, and domain-specific standards of knowledge. It can also support TOK Exhibition planning and essay discussion on how evidence is evaluated in different Areas of Knowledge.