Scientific Method

The scientific method is the loose family of practices by which claims about the natural world are proposed, tested against observation and revised. Textbooks present it as a fixed sequence: observe, form a hypothesis, predict, experiment, analyze, conclude. Working scientists rarely follow that order, and many historians of science doubt that any single method exists. The core idea is stable all the same: an idea earns belief by surviving tests it could have failed.

The roots are old. Aristotle catalogued animals and reasoned from observation. The eleventh-century scholar Ibn al-Haytham tested claims about light and vision with controlled experiments. Francis Bacon, in 1620, urged natural philosophers to build general laws from carefully gathered particulars rather than from ancient authority. Generalizing from instances runs into the problem of induction, though: no number of white swans proves that all swans are white.

The usual modern framing is the hypothetico-deductive method. A scientist proposes a hypothesis, deduces what should be observed if it's true, and checks. A confirmed prediction lends support but never proof. A failed one counts against the hypothesis, unless the fault lies in an auxiliary assumption, such as a miscalibrated instrument. Karl Popper made this asymmetry the dividing line between science and pseudoscience, arguing that a theory no observation could contradict says nothing about the world; see Falsifiability. When several hypotheses fit the evidence equally well, scientists tend to prefer the one that assumes least; see Occam's Razor.

Testing needs measurement, and abstract ideas like stress or intelligence must be turned into something countable before they can be tested. The strongest test of a cause is an experiment in which the experimenter assigns the treatment at random, so that on average nothing else differs between the groups. Where experiments are impossible, as in astronomy or much of epidemiology, careful observation and accidents of circumstance must stand in. Some questions are settled by reasoning before any apparatus is built.

The method is also social. Other experts check results before publication, and findings count for most once someone else has reproduced them. The replication crisis showed how badly that checking can fail when flexible analysis and publication pressure reward surprising results. Committing to a hypothesis and an analysis plan before collecting data is one attempt to repair it.

Thomas Kuhn argued that most science happens within an accepted framework, which researchers abandon only when anomalies pile up, so progress comes in revolutions rather than smooth accumulation. On that view the method itself changes over time, as each field settles what counts as evidence. Statistics, controlled trials and computer simulation were all once new additions to it.