The Oxford Companion to Philosophy, 1995
ABDUCTION. Abductive reasoning accepts a conclusion on the grounds that it explains the available evidence. The term was introduced by Charles Peirce to describe an inference pattern sometimes called ‘hypothesis’ or *’inference to the best explanation’. He used the example of arriving at a Turkish seaport and observing a man on horseback surrounded by horsemen holding a canopy over his head. He inferred that this was the governor of the province since he could think of no other figure who would be so greatly honoured. In his later work, Peirce used the word more widely: the logic of abduction examines all of the norms which guide us in formulating new hypotheses and deciding which of them to take seriously. It addresses a wide range of issues concerning the ‘logic of discovery’ and the economics of research.
AI (ChatGPT 5.2, prompt: Explain: abduction)
Abduction is a form of reasoning where you infer the most plausible explanation for an observation.
Structure:
• You observe a surprising fact.
• If hypothesis H were true, the fact would make sense.
• Therefore, H is a reasonable explanation.
It does not prove H is true. It proposes a candidate explanation.
Example:
• The ground is wet.
• If it rained last night, the ground would be wet.
• So, it probably rained last night.
That is abduction.
Contrast with the other two main forms of reasoning:
• Deduction: From general rule to certain conclusion. If the premises are true, the conclusion must be true.
• Induction: From repeated cases to a general rule. The conclusion is probable.
• Abduction: From an effect to a possible cause. The conclusion is a hypothesis.
Key points:
• Abduction is explanatory, not demonstrative.
• It is common in science, diagnosis, everyday reasoning, and philosophy.
• Charles Sanders Peirce formalized it as a third, irreducible type of inference.
In short:
Abduction is reasoning to the best explanation, under uncertainty.
Wikipedia
Abductive reasoning (also called abduction, abductive inference, or retroduction) is a form of logical inference that seeks the simplest and most likely conclusion from a set of observations. It was formulated and advanced by the American philosopher and logician Charles Sanders Peirce beginning in the latter half of the 19th century.
Abductive reasoning, unlike deductive reasoning, yields a plausible conclusion but does not definitively verify it. Abductive conclusions do not eliminate uncertainty or doubt, which is expressed in terms such as “best available” or “most likely”. While inductive reasoning draws general conclusions that apply to many situations, abductive conclusions are confined to the particular observations in question.
In his own words
Collected papers. Charles Sanders Peirce
Peirce: CP 2.623 Cross-Ref: TT
- But this is not the only way of inverting a deductive syllogism so as to produce a synthetic inference. Suppose I enter a room and there find a number of bags, containing different kinds of beans. On the table there is a handful of white beans; and, after some searching, I find one of the bags contains white beans only. I at once infer as a probability, or as a fair guess, that this handful was taken out of that bag. This sort of inference is called making an hypothesis. It is the inference of a case from a rule and a result. We have, then–
DEDUCTION.
Rule.–All the beans from this bag are white.
Case.–These beans are from this bag.
Result.–These beans are white.
INDUCTION.
Case.–These beans are from this bag.
Result.–These beans are white.
Rule.–All the beans from this bag are white
HYPOTHESIS.
Rule.–All the beans from this bag are white.
Result.–These beans are white.
Case.–These beans are from this bag.
Peirce: CP 5.171 Cross-Ref:TT 84. INSTINCT AND ABDUCTION T1
- Concerning the validity of Abductive inference, there is little to be said, although that little is pertinent to the problem we have in hand.
Abduction is the process of forming an explanatory hypothesis. It is the only logical operation which introduces any new idea; for induction does nothing but determine a value, and deduction merely evolves the necessary consequences of a pure hypothesis.
Deduction proves that something must be; Induction shows that something actually is operative; Abduction merely suggests that something may be.
Its only justification is that from its suggestion deduction can draw a prediction which can be tested by induction, and that, if we are ever to learn anything or to understand phenomena at all, it must be by abduction that this is to be brought about.
No reason whatsoever can be given for it, as far as I can discover; and it needs no reason, since it merely offers suggestions.
A man must be downright crazy to deny that science has made many true discoveries. But every single item of scientific theory which stands established today has been due to Abduction.
You find this work here on the interner archive: https://archive.org/details/collected-papers-of-charles-peirce/page/n541/mode/2up
Charles Sanders Peirce; September 10, 1839 – April 19, 1914) was an American scientist, mathematician, logician, and philosopher who is sometimes known as “the father of pragmatism”.According to philosopher Paul Weiss, Peirce was “the most original and versatile of America’s philosophers and America’s greatest logician”.Bertrand Russell wrote “he was one of the most original minds of the later nineteenth century and certainly the greatest American thinker ever”.
Educated as a chemist and employed as a scientist for thirty years, Peirce made major contributions to logic, such as theories of relations and quantification. C. I. Lewis wrote, “The contributions of C. S. Peirce to symbolic logic are more numerous and varied than those of any other writer—at least in the nineteenth century.” For Peirce, logic also encompassed much of what is now called epistemology and the philosophy of science. He saw logic as the formal branch of semiotics or study of signs, of which he is a founder, which foreshadowed the debate among logical positivists and proponents of philosophy of language that dominated 20th-century Western philosophy. Peirce’s study of signs also included a tripartite theory of predication.
Additionally, he defined the concept of abductive reasoning, as well as rigorously formulating mathematical induction and deductive reasoning. He was one of the founders of statistics. As early as 1886, he saw that logical operations could be carried out by electrical switching circuits. The same idea was used decades later to produce digital computers.
The thought process is an interesting read. I guess the makers had some fun programming this in it..
Nochrisis 