The idea that the simplest, most easily verifiable solution should be preferred over its more complicated counterparts is a very old one. To this point,
George Pólya, in his treatise on problem-solving, makes reference to the following Latin truism:
simplex sigillum veri (simplicity is the seal of truth).
Introduction and development by Peirce Overview The American philosopher Charles Sanders Peirce introduced abduction into modern logic. Over the years he called such inference
hypothesis,
abduction,
presumption, and
retroduction. He considered it a topic in logic as a normative field in philosophy, not in purely formal or mathematical logic, and eventually as a topic also in economics of research. As two stages of the development, extension, etc., of a hypothesis in scientific
inquiry, abduction and also
induction are often collapsed into one overarching concept—the hypothesis. That is why, in the
scientific method known from
Galileo and
Bacon, the abductive stage of hypothesis formation is conceptualized simply as induction. Thus, in the twentieth century this collapse was reinforced by
Karl Popper's explication of the
hypothetico-deductive model, where the hypothesis is considered to be just "a guess" (in the spirit of Peirce). However, when the formation of a hypothesis is considered the result of a process it becomes clear that this "guess" has already been tried and made more robust in thought as a necessary stage of its acquiring the status of hypothesis. Indeed, many abductions are rejected or heavily modified by subsequent abductions before they ever reach this stage. Before 1900, Peirce treated abduction as the use of a known rule to explain an observation. For instance: it is a known rule that, if it rains, grass gets wet; so, to explain the fact that the grass on this lawn is wet, one
abduces that it has rained. Abduction can lead to false conclusions if other rules that might explain the observation are not taken into accounte.g. the grass could be wet from
dew. This remains the common use of the term "abduction" in the
social sciences and in
artificial intelligence. Peirce consistently characterized it as the kind of inference that originates a hypothesis by concluding in an explanation, though an unassured one, for some very curious or surprising (anomalous) observation stated in a premise. As early as 1865 he wrote that all conceptions of cause and force are reached through hypothetical inference; in the 1900s he wrote that all explanatory content of theories is reached through abduction. In other respects Peirce revised his view of abduction over the years. In later years his view came to be: • Abduction is guessing. It is "very little hampered" by rules of logic. Even a well-prepared mind's individual guesses are more frequently wrong than right. But the success of our guesses far exceeds that of random luck and seems born of attunement to nature by instinct (some speak of
intuition in such contexts). • Abduction guesses a new or outside idea so as to account in a plausible, instinctive, economical way for a surprising or very complicated phenomenon. That is its proximate aim. Its rationale especially involves its role in coordination with other modes of inference in inquiry. It is inference to explanatory hypotheses for selection of those best worth trying. •
Pragmatism is the logic of abduction. Upon the generation of an explanation (which he came to regard as instinctively guided), the
pragmatic maxim gives the necessary and sufficient logical rule to abduction in general. The hypothesis, being insecure, needs to have conceivable implications for informed practice, so as to be testable and, through its trials, to expedite and economize inquiry. The economy of research is what calls for abduction and governs its art. Writing in 1910, Peirce admits that "in almost everything I printed before the beginning of this century I more or less mixed up hypothesis and induction" and he traces the confusion of these two types of reasoning to logicians' too "narrow and formalistic a conception of inference, as necessarily having formulated judgments from its premises." He started out in the 1860s treating hypothetical inference in a number of ways which he eventually peeled away as inessential or, in some cases, mistaken: • as inferring the occurrence of a character (a characteristic) from the observed combined occurrence of multiple characters which its occurrence would necessarily involve; for example, if any occurrence of
A is known to necessitate occurrence of
B, C, D, E, then the observation of
B, C, D, E suggests by way of explanation the occurrence of
A. (But by 1878 he no longer regarded such multiplicity as common to all hypothetical inference.Wikisource) • as aiming for a more or less probable hypothesis (in 1867 and 1883 but not in 1878; anyway by 1900 the justification is not probability but the lack of alternatives to guessing and the fact that guessing is fruitful; by 1903 he speaks of the "likely" in the sense of nearing the truth in an "indefinite sense"; by 1908 he discusses
plausibility as instinctive appeal. • as induction from characters (but as early as 1900 he characterized abduction as guessing) • as basically a transformation of a deductive categorical syllogism).
The Natural Classification of Arguments (1867) In Peirce's
On the Natural Classification of Arguments (1867), Like
Deduction, Induction, and Hypothesis in 1878, it was widely read (see the historical books on statistics by
Stephen Stigler), unlike his later amendments of his conception of abduction. Today abduction remains most commonly understood as induction from characters and extension of a known rule to cover unexplained circumstances.
Sherlock Holmes used this method of reasoning in the stories of
Arthur Conan Doyle, although Holmes refers to it as "
deductive reasoning".
Minute Logic (1902) and after In 1902 Peirce wrote that he now regarded the syllogistical forms and the doctrine of extension and comprehension (i.e., objects and characters as referenced by terms), as being less fundamental than he had earlier thought. In 1903 he offered the following form for abduction: In 1903 Peirce called
pragmatism "the logic of abduction" and said that the
pragmatic maxim gives the necessary and sufficient logical rule to abduction in general. he said that the conduct of abduction (or retroduction) is governed by considerations of economy, belonging in particular to the economics of research. He regarded economics as a normative science whose analytic portion might be part of logical methodeutic (that is, theory of inquiry).
Three levels of logic about abduction Peirce came over the years to
divide (philosophical) logic into three departments: • Stechiology, or speculative grammar, on the conditions for meaningfulness. Classification of signs (semblances, symptoms, symbols, etc.) and their combinations (as well as their objects and
interpretants). • Logical critic, or logic proper, on validity or justifiability of inference, the conditions for true representation. Critique of arguments in their various modes (deduction, induction, abduction). • Methodeutic, or speculative rhetoric, on the conditions for determination of interpretations. Methodology of inquiry in its interplay of modes. Peirce had, from the start, seen the modes of inference as being coordinated together in scientific inquiry and, by the 1900s, held that hypothetical inference in particular is inadequately treated at the level of critique of arguments. Peirce held that: • Hypothesis (abductive inference) is inference through an
icon (also called a
likeness). • Induction is inference through an
index (a sign by factual connection); a sample is an index of the totality from which it is drawn. • Deduction is inference through a
symbol (a sign by interpretive habit irrespective of resemblance or connection to its object). In 1902, Peirce wrote that, in abduction: "It is recognized that the phenomena are
like, i.e. constitute an Icon of, a replica of a general conception, or Symbol."
Critique of arguments At the critical level Peirce examined the forms of abductive arguments (as discussed above), and came to hold that the hypothesis should economize explanation for plausibility in terms of the feasible and natural. In 1908 Peirce described this plausibility in some detail. For Peirce, plausibility does not depend on observed frequencies or probabilities, or on verisimilitude, or even on testability, which is not a question of the critique of the hypothetical inference
as an inference, but rather a question of the hypothesis's relation to the inquiry process. The phrase "inference to the best explanation" (not used by Peirce but often applied to hypothetical inference) is not always understood as referring to the most simple and natural hypotheses (such as those with the
fewest assumptions). However, in other senses of "best", such as "standing up best to tests", it is hard to know which is the best explanation to form, since one has not tested it yet. Still, for Peirce, any justification of an abductive inference as "good" is not completed upon its formation as an argument (unlike with induction and deduction) and instead depends also on its methodological role and promise (such as its testability) in advancing inquiry.
Methodology of inquiry At the methodeutical level Peirce held that a hypothesis is judged and selected
Uberty Peirce indicated that abductive reasoning is driven by the need for "economy in research"—the expected fact-based productivity of hypotheses, prior to deductive and inductive processes of verification. A key concept proposed by him in this regard is "
uberty"—the expected fertility and pragmatic value of reasoning. This concept seems to be gaining support via association to the
Free Energy Principle.
Gilbert Harman (1965) Gilbert Harman was a professor of philosophy at
Princeton University. Harman's 1965 account of the role of "inference to the best explanation" – inferring the existence of that which we need for the best explanation of observable phenomena – has been very influential.
Stephen Jay Gould (1995) Stephen Jay Gould, in answering the
Omphalos hypothesis, claimed that only hypotheses that can be proved incorrect lie within the domain of
science and only these hypotheses are good explanations of facts worth inferring to. ==Applications==