Facts and evidence
Scientific knowledge begins from observations and measurements that can be checked, reproduced or independently constrained.
ObservationReliable description begins from phenomena that can be recorded.
MeasurementQuantitative measurements require defined units, procedures and uncertainties.
ReproducibilityIndependent checks reduce the chance that a result depends on unnoticed local conditions.
EvidenceA single fact may support several explanations; evidence becomes decisive when alternatives predict different outcomes.