• Unsourced variant: Evolution is not a fact. Evolution doesn't even qualify as a theory or as a hypothesis. It is a metaphysical research program, and it is not really testable science.
Popper later retracted his criticisms:" - Meaning and context.">
QuotesCosmos
I have changed my mind about the testability and logical status of the theory of natural selection; and I am glad to have an opportunity to make a recantation.
 • "Natural selection and the emergence of mind" dialectica Vol. 32 (1978), p. 339-355; republished in Evolutionary Epistemology, Rationality, and the Sociology of Knowledge (1987) edited by Gerard Radnitzky and W. W. Bartley, III
“

Darwinism is not a testable scientific theory, but a metaphysical research program.
• Unsourced variant: Evolution is not a fact. Evolution doesn't even qualify as a theory or as a hypothesis. It is a metaphysical research program, and it is not really testable science.
Popper later retracted his criticisms:

— Karl Popper

What It Means

This is a placeholder explanation generated by the low-overhead model. It interprets "Darwinism is not a testable scientific theory, but a metaphysical research program.
• Unsourced variant: Evolution is not a fact. Evolution doesn't even qualify as a theory or as a hypothesis. It is a metaphysical research program, and it is not really testable science.
Popper later retracted his criticisms:" in the context of "I have changed my mind about the testability and logical status of the theory of natural selection; and I am glad to have an opportunity to make a recantation.
 • "Natural selection and the emergence of mind" dialectica Vol. 32 (1978), p. 339-355; republished in Evolutionary Epistemology, Rationality, and the Sociology of Knowledge (1987) edited by Gerard Radnitzky and W. W. Bartley, III" to mean that wisdom is timeless.

Quote Image
Source: Wikiquote: "Karl Popper" (Quotes, Unended Quest: An Intellectual Autobiography (1976)) The 'What it means' explanation text was generated by Google Gemini Flash (accessed January 18, 2026). https://gemini.google.com/app

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Karl Popper

About Karl Popper

Sir Karl Raimund Popper (28 July 1902 – 17 September 1994) was an Austrian-British philosopher, academic and social commentator. One of the 20th century's most influential philosophers of science, Popper is known for his rejection of the classical inductivist views on the scientific method in favour of empirical falsification. According to Popper, a theory in the empirical sciences can never be proven, but it can be falsified, meaning that it can (and should) be scrutinised with decisive experiments. Popper was opposed to the classical justificationist account of knowledge, which he replaced with critical rationalism, namely "the first non-justificational philosophy of criticism in the history of philosophy".