Pessimistic induction
Encyclopedia
In the philosophy of science
Philosophy of science
The philosophy of science is concerned with the assumptions, foundations, methods and implications of science. It is also concerned with the use and merit of science and sometimes overlaps metaphysics and epistemology by exploring whether scientific results are actually a study of truth...

, the pessimistic induction, also known as the pessimistic meta-induction, is an argument which seeks to rebut scientific realism
Scientific realism
Scientific realism is, at the most general level, the view that the world described by science is the real world, as it is, independent of what we might take it to be...

, particularly the scientific realist's notion of epistemic optimism.

Scientific realists argue that we have good reasons to believe that our presently successful scientific theories are true or approximately true, where approximate truth means a theory is able to make novel predictions and that the central terms of such theories genuinely refer. The pessimistic meta-induction undermines the realist's warrant for his epistemic optimism via historical counterexample. Larry Laudan
Larry Laudan
Larry Laudan is a contemporary philosopher of science and epistemologist. He has strongly criticized the traditions of positivism, realism, and relativism, and he has defended a view of science as a privileged and progressive institution against popular challenges...

 argues that the history of science is a "graveyard" of once empirically successful theories whose central terms have been found not to refer. For example, 18th century optical aether theory and the humoral theory of medicine
Humorism
Humorism, or humoralism, is a now discredited theory of the makeup and workings of the human body, adopted by Greek and Roman physicians and philosophers, positing that an excess or deficiency of any of four distinct bodily fluids in a person directly influences their temperament and health...

 were incredibly successful, and yet we no longer believe in the existence of aether
Aether
-Metaphysics and mythology:* Aether , the material that fills the region of the universe above the terrestrial sphere* Aether was the personification of the "upper sky", space and heaven, in Greek mythology-Science and engineering:...

, nor would we want to label such theories as having been approximately true. Using meta-induction
Inductive reasoning
Inductive reasoning, also known as induction or inductive logic, is a kind of reasoning that constructs or evaluates propositions that are abstractions of observations. It is commonly construed as a form of reasoning that makes generalizations based on individual instances...

, Laudan then argues that if past scientific theories which were successful were found to be false, we have no reason to believe the realist's claim that our currently successful theories are approximately true. The pessimistic meta-induction argument was first fully postulated by Laudan in 1981 and survives to this day as one of the strongest arguments against scientific realism.

However, there are some objections against Laudan's theory. One might see shortcomings in the historic examples Laudan gives as proof of his hypothesis. Theories like cristalline spheres astronomy, or the phlogiston theory
Phlogiston theory
The phlogiston theory , first stated in 1667 by Johann Joachim Becher, is an obsolete scientific theory that postulated the existence of a fire-like element called "phlogiston", which was contained within combustible bodies and released during combustion...

do not represent the most successful theories at their time. A further objection tries to point out that in scientific progress we indeed approximate the truth. When we develop a new theory, the central ideas of the old one usually become refuted. Parts of the old theory, however, we carry over to the new one. In doing so, our theories become more and more well-founded on other principles, they become better in terms of predictive and descriptive power etc. Therefore, we can hold the realist view that our theoretical terms refer to something in the world and our theories are approximately true.
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