Observation, experiment, and measurement provide the empirical evidence used to formulate, test, and revise scientific claims. However, they do not produce completely neutral facts: scientific evidence is selected and interpreted through concepts, theories, instruments, and methodological assumptions.
| Method | Role in science | Philosophical issue |
|---|---|---|
| Observation | Records phenomena and identifies patterns that may require explanation. | Observations may be theory-laden, meaning prior beliefs and concepts influence what scientists notice and how they describe it. |
| Experiment | Manipulates an independent variable under controlled conditions to test its effect on a dependent variable. | Complete control may be impossible, while some subjects, such as ecosystems or distant galaxies, cannot be tested through controlled experiments. |
| Measurement | Represents properties using standardized quantities, allowing precise comparison, replication, and mathematical analysis. | Instruments have limits, measurement uncertainty, and may partly determine what can count as evidence. |
These methods support empiricism, the view that knowledge depends fundamentally on sense experience. Observation may generate a hypothesis; an experiment then tests a prediction derived from it; measurement produces quantitative data against which the prediction can be assessed.
However, evidence does not automatically prove a theory. According to Karl Popper, scientific theories should be falsifiable: they must make predictions that could, in principle, be shown false. Confirming observations can support a theory, but they cannot establish its universal truth because of the problem of induction. Observing many metals expanding when heated does not logically guarantee that every metal will always do so.
A further issue is underdetermination: the same evidence may be compatible with more than one explanation. Scientists therefore also use criteria such as explanatory power, simplicity, predictive success, and coherence with existing knowledge.
For an IB Philosophy response, do not merely state that science “uses evidence.” Explain each method, then evaluate whether evidence is objective and sufficient to justify scientific knowledge. A strong answer uses a philosopher such as Popper and considers theory-ladenness, induction, or underdetermination.
