The scientific method is a systematic framework for acquiring empirical knowledge through structured observation, hypothesis formation, experimentation, and revision. It is not a single fixed procedure but a family of overlapping practices unified by a commitment to evidence-based reasoning and, in most formulations, the principle that claims must be falsifiable or at minimum testable against the world. The method developed incrementally from ancient natural philosophy and took its modern form largely during the Scientific Revolution of the 16th and 17th centuries; for a detailed account see Scientific Method - History.

Most descriptions of the scientific method include some combination of the following elements: observation of a phenomenon, formulation of a question, construction of a hypothesis or model, design of an experiment or observational study to test predictions derived from that hypothesis, collection and analysis of data, and revision or rejection of the hypothesis in light of results. This cycle is iterative; results generate new observations and new questions. Peer review, replication by independent researchers, and publication of methods and data are institutional practices that complement the core logical structure and serve as checks against error and fraud.

The exact logical structure of scientific inference is contested among philosophers of science. Karl Popper argued that science advances by falsification - a claim is scientific only if it is in principle refutable by evidence - and that no quantity of confirming instances can logically verify a universal claim. W.V.O. Quine and Pierre Duhem observed that individual hypotheses are never tested in isolation; auxiliary assumptions are always present, so a failed prediction does not unambiguously refute a single claim. Thomas Kuhn described science as operating within paradigms - shared frameworks of assumptions and exemplars - that are replaced during periods of revolutionary change rather than corrected piecemeal. Imre Lakatos synthesized elements of Popper and Kuhn in his account of competing research programmes. These interpretive disputes belong to philosophy of science and do not undermine routine scientific practice, though they bear on contested boundary cases.

Different scientific disciplines apply the method's components in different proportions. Experimental sciences such as physics, chemistry, and molecular biology rely heavily on controlled laboratory experiments in which variables can be isolated. Observational sciences such as astronomy, paleontology, epidemiology, and much of geology and ecology work primarily with data they cannot fully control, relying on statistical inference, natural experiments, and convergent evidence from multiple independent lines. Social and behavioral sciences face additional complications from reflexivity (subjects who respond to being studied), the difficulty of blinding, and the near-impossibility of controlled experiments on many questions of interest. These structural differences produce ongoing methodological debate within and across disciplines.

Beginning in the early 2010s, large-scale replication efforts across several fields - including social psychology, cancer biology, nutrition science, and economics - found that a substantial proportion of published findings could not be reproduced by independent teams following the same protocols. Estimates of replication failure rates vary widely by field and methodology; see Replication Crisis for detailed figures. Proposed causes include publication bias toward positive results, underpowered studies, p-hacking and other flexible analytic practices, inadequate reporting of methods, and incentive structures in academic publishing and funding that reward novelty over rigor. The replication crisis has prompted methodological reform efforts, including pre-registration of hypotheses and analysis plans, open data and materials requirements, and increased use of multi-site studies.

The demarcation problem - distinguishing science from non-science and pseudoscience - remains philosophically unresolved. No single criterion proposed to date cleanly separates all cases. Falsifiability, empirical testability, mechanism, and predictive success are commonly invoked criteria, each with acknowledged counterexamples at the margins. Applied to contested fields, different demarcation criteria yield different classifications, and these disagreements have practical stakes in areas such as public policy, legal proceedings, and education.

There is broad agreement among philosophers and practitioners of science that the method's core commitments - empirical testing, revision in light of evidence, and transparency of methods - distinguish scientific inquiry from other epistemological traditions. No consensus exists on the correct philosophical account of why the method works, whether it converges on truth, or precisely where its boundaries lie. See Scientific Method - Philosophy Consensus for the extent of agreement on foundational questions.

• Popperian falsificationism holds that falsifiability is the necessary criterion of scientific status and that science advances solely by elimination of false hypotheses rather than confirmation of true ones. Popperian Falsificationism Viewpoint

• Kuhnian paradigm theory holds that science operates within socially shared paradigms and advances through revolutionary replacement rather than continuous accumulation. Kuhnian Paradigm Theory Viewpoint

• Bayesian confirmation theory holds that scientific reasoning is best understood as updating probability assignments over hypotheses in light of evidence, and that confirmation is a matter of degree rather than all-or-nothing falsification. Bayesian Confirmation Theory Viewpoint

• Scientific realism holds that successful scientific theories are approximately true descriptions of an observer-independent reality, including unobservable entities. Scientific Realism Viewpoint

• Anti-realism and instrumentalism holds that scientific theories are tools for predicting observations and need not be interpreted as literal descriptions of unobservable reality. Anti-Realism and Instrumentalism Viewpoint

• Feminist and social epistemology critiques hold that social position, funding sources, and cultural assumptions shape which questions get asked and which methods get treated as rigorous, and that standard accounts of the method fail to make these influences visible. Social Epistemology Critique Viewpoint

• Scientific Method - History
• Scientific Method - Debate
• Scientific Method - Philosophy Consensus
• Scientific Revolution
• Demarcation Problem
• Replication Crisis
• Peer Review
• Philosophy of Science

1. Popper, Karl. The Logic of Scientific Discovery. Hutchinson, 1959. Originally published as Logik der Forschung, 1934.
2. Kuhn, Thomas S. The Structure of Scientific Revolutions. University of Chicago Press, 1962.
3. Duhem, Pierre. The Aim and Structure of Physical Theory. Princeton University Press, 1954. Originally published 1906.
4. Quine, W.V.O. “Two Dogmas of Empiricism.” The Philosophical Review 60, no. 1 (1951): 20-43.
5. Lakatos, Imre. “Falsification and the Methodology of Scientific Research Programmes.” In Criticism and the Growth of Knowledge, edited by Lakatos and Musgrave. Cambridge University Press, 1970.
6. Open Science Collaboration. “Estimating the Reproducibility of Psychological Science.” Science 349, no. 6251 (2015): aac4716.
7. Begley, C. Glenn, and Lee M. Ellis. “Drug Development: Raise Standards for Preclinical Cancer Research.” Nature 483 (2012): 531-533.
8. Nosek, Brian A., et al. “Promoting an Open Research Culture.” Science 348, no. 6242 (2015): 1422-1425.