Falsifiability: Karl Popper's Basic Scientific Principle

Originally published on https://explorable.com/falsifiability 

Falsifiability, as defined by the philosopher, Karl Popper, defines the inherent testability of any scientific hypothesis.

Science and philosophy [1] have always worked together to try to uncover truths [2] about the world and the universe around us. Both are a necessary element for the advancement of knowledge and the development of human society.

Scientists design experiments [3] and try to obtain results verifying or disproving a hypothesis, but philosophers are the driving force in determining what factors determine the validity [4] of scientific results.

Often, they even determine the nature of science itself and influence the direction of viable research. As one theory is falsified, another evolves to replace it and explain the new observations.

One of the tenets behind science is that any scientific hypothesis [5] and resultant experimental design must be inherently falsifiable. Although falsifiability is not universally accepted, it is still the foundation of the majority of scientific experiments.

What is Falsifiability?

In its basic form, falsifiability is the belief that for any hypothesis to have credence, it must be inherently disprovable before it can become accepted as a scientific hypothesis or theory.

For example, if a scientist asks, "Does God exist?" then this can never be science because it is a theory that cannot be disproved.
The idea is that no theory is completely correct [2], but if not falsified, it can be accepted as truth.

For example, Newton's Theory of Gravity was accepted as truth for centuries, because objects do not randomly float away from the earth. It appeared to fit the figures obtained by experimentation [6] and research [7], but was always subject to testing.

However, Einstein's theory makes falsifiable predictions that are different from predictions made by Newton's theory, for example concerning the precession of the orbit of Mercury, and gravitational lensing of light. In non-extreme situations Einstein's and Newton's theories make the same predictions, so they are both correct. But Einstein's theory holds true in a superset of the conditions in which Newton's theory holds, so according to the principle of Occam's Razor [8], Einstein's theory is preferred. On the other hand, Newtonian calculations are simpler, so Newton's theory is useful for almost any engineering project, including some space projects. But for GPS we need Einstein's theory.

Popper saw falsifiability as a black and white definition, that if a theory is falsifiable, it is scientific [9], and if not, then it is unscientific. Whilst most 'pure' sciences do adhere to this strict definition, pseudo-sciences [10] may fall somewhere between the two extremes.

Pseudo Science

According to Popper, many branches of applied science, especially social science, are not scientific because they have no potential for falsification.

Anthropology and sociology, for example, often use case studies [11] to observe people in their natural environment without actually testing [12] any specific hypotheses or theories.

Whilst such studies and ideas are not falsifiable, most would agree that they are scientific because they significantly advance human knowledge.

Even 'pure' or 'true' science must make compromises and assumptions on occasion. The testing of any theory must take into account the equipment and resources available.

Falsifiability is not a simple black and white matter because a theory, which is difficult to falsify at the time, may be falsified in the future.

The Raven Paradox [13] shows the inherent danger of relying on falsifiability, because very few scientific experiments can measure all of the data, and rely upon generalization [14].


For many of the pure sciences, the idea of falsifiability is a useful tool for generating theories that are testable and realistic.

If a falsifiable theory is tested and the results are significant [15], then it can become accepted as a scientific truth.

The advantage of Popper's idea is that such truths can be falsified when more knowledge and resources are available. Even long accepted theories such as Gravity, Relativity and Evolution are increasingly challenged and adapted.

The major disadvantage of falsifiability is that it is very strict in its definitions and does not take into account that many sciences are observational [16] and descriptive [17].

Source URL: https://explorable.com/falsifiability

[1] https://explorable.com/philosophy-of-science,
[2] https://explorable.com/truth-and-theory,
[3] https://explorable.com/design-of-experiment,
[4] https://explorable.com/types-of-validity,
[5] https://explorable.com/research-hypothesis,
[6] https://explorable.com/conducting-an-experiment,
[7] https://explorable.com/what-is-research,
[8] http://explorable.com/occams-razor,
[9] https://explorable.com/what-is-the-scientific-method,
[10] https://explorable.com/pseudoscience,
[11] https://explorable.com/case-study-research-design,
[12] https://explorable.com/hypothesis-testing,
[13] https://explorable.com/raven-paradox,
[14] https://explorable.com/what-is-generalization,
[15] https://explorable.com/statistically-significant-results,
[16] https://explorable.com/observational-study,
[17] https://explorable.com/descriptive-research-design,
[18] https://explorable.com/users/martyn,
[19] https://explorable.com/falsifiability