- Hunch – a wordlessly sensed possibility
- Intuition – a hunch made articulate (gate: articulation)
- Hypothesis – an intuition supported by informal evidence (gate: evidence)
- Experiment – a hypothesis put in testable form (gate: operationalized as test)
- Theory – an experimentally-confirmed hypothesis (gate: affirmed by test)
- Fact – a theory that has been tested sufficiently that a community regards it as true (gate: community acceptance)