Pseudoscience consists of statements, beliefs, or practices that claim to be both scientific and factual but are incompatible with the scientific method. Pseudoscience is often characterized by contradictory, exaggerated or unfalsifiable claims; reliance on confirmation bias rather than rigorous attempts at refutation; lack of openness to evaluation by other experts; absence of systematic practices when developing hypotheses; and continued adherence long after the pseudoscientific hypotheses have been experimentally discredited.The demarcation between science and pseudoscience has philosophical, political, and scientific implications. Differentiating science from pseudoscience has practical implications in the case of health care, expert testimony, environmental policies, and science education. Distinguishing scientific facts and theories from pseudoscientific beliefs, such as those found in climate change denial, astrology, alchemy, alternative medicine, occult beliefs, and creation science, is part of science education and literacy.Pseudoscience can have dangerous effects. For example, pseudoscientific anti-vaccine activism and promotion of homeopathic remedies as alternative disease treatments can result in people forgoing important medical treatments with demonstrable health benefits, leading to deaths and ill-health. Furthermore, people who refuse legitimate medical treatments to contagious diseases may put others at risk. Pseudoscientific theories about racial and ethnic classifications have led to racism and genocide.
The term pseudoscience is often considered pejorative particularly by purveyors of it, because it suggests something is being presented as science inaccurately or even deceptively. Those practicing or advocating pseudoscience therefore frequently dispute the characterization.