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Recent developments in the cognitive sciences and artificial intelligence suggest ways of answering the most serious challenge to Peirce's notion of abduction. Either there is no such logical process as abduction or, if abduction is a form of inference, it is essentially unconscious and therefore beyond rational control so that it lacks any normative significance. Peirce himself anticipates and attempts to answer this challenge. Peirce argues that abduction is both a source of creative insight and a form of logical inference subject to a degree of conscious control. In this paper I shall sketch a developing account of abduction that is suggested by the work of Paul Churchland, Paul Thagard, Chris Eliasmith, William Wimsatt, Owen Flanagan, and others. I shall argue that a credible account of abduction will require that we approach the phenomenon from both higher and lower levels as represented by these approaches.

Jaakko Hintikka (1998) has argued that clarifying the notion of abduction is the fundamental problem of contemporary epistemology. One traditional interpretation of Peirce on abduction sees it as a recipe for generating new theoretical discoveries . A second standard view sees abduction as a mode of reasoning that justifies beliefs about the probable truth of theories. While each reading has some grounding in Peirce's writings, each leaves out features that are crucial to Peirce's distinctive understanding of abduction. I develop and defend a third interpretation, according to which Peirce takes abductive reasoning to lead to judgments about the relative pursuitworthiness of theories; conclusions that can be thoroughly disconnected from assessments of truth-value. Even if Peirce's use of "abduction" slides around among each of these three importantly different though potentially compatible senses, this neglected third understanding makes sense of a large number of Peirce's remarks and directs our attention to the cognitive structure of judgments that scientists face after the initial proposal of explanatory hypotheses but prior to their experimental testing; a topic which should be of interest to contemporary philosophers of science.

I argue against the tendency in the philosophy of science literature to link abduction to the inference to the best explanation (IBE), and in particular, to claim that Peircean abduction is a conceptual predecessor to IBE. This is not to discount either abduction or IBE. Rather the purpose of this paper is to clarify the relation between Peircean abduction and IBE in accounting for ampliative inference in science. This paper aims at a proper classification—not justification—of types of scientific reasoning. In particular, I claim that Peircean abduction is an in-depth account of the process of generating explanatory hypotheses, while IBE, at least in Peter Lipton’s thorough treatment, is a more encompassing account of the processes both of generating and of evaluating scientific hypotheses. There is then a two-fold problem with the claim that abduction is IBE. On the one hand, it conflates abduction and induction, which are two distinct forms of logical inference, with two distinct aims, as shown by Charles S. Peirce; on the other hand it lacks a clear sense of the full scope of IBE as an account of scientific inference.

Peirce presented early formulations of abductive inference nearly 150 years ago. Since then new interpretations have been presented (some of them quite independently of Peirce), but there is still a close link to Peirce’s formulations. Lorenzo Magnani has written a new book on abduction where the main theme is not Peirce’s interpretation of abduction as such, but the book is very interesting from the Peircean perspective. In this review I shall focus on some of the themes from this point of view. Magnani presents a broad view on abduction instead of presenting only one specific interpretation of abduction. This reflects the history of abduction. Peirce’s writings themselves give elements for various ..

One of the most pressing issues in understanding abduction is whether it is an instinct or an inference. For many commentators find it paradoxical that new ideas are products of an instinct and products of an inference at the same time. Fortunately, Lorenzo Magnani’s recent discussion of animal abduction sheds light on both instinctual and inferential character of Peircean abduction. But, exactly for what reasons are Peirce and Magnani so convinced that animal abduction can provide us with a novel perspective? Inspired by Peirce’s and Magnani’s discussions of animal abduction, I propose to compare Peirce’s and Magnani’s views of animal abduction with the estimative power of non-human animals and humans, which was one of the internal senses in medieval psychology.

Charles S. Peirce argued that, besides deduction and induction, there is a third mode of inference which he called "hypothesis" or "abduction." He characterized abduction as reasoning "from effect to cause," and as "the operation of adopting an explanatory hypothesis." Peirce's ideas about abduction, which are related also to historically earlier accounts of heuristic reasoning (the method of analysis), have been seen as providing a logic of scientific discovery. Alternatively, abduction is interpreted as giving reasons for pursuing a hypothesis. Inference to the best explanation (IBE) has also been regarded as an important mode of justification, both in everyday life, detective stories, and science. In particular, scientific realism has been defended by an abductive nomiracle argument (Smart, Putnam, Boyd), while the critics of realism have attempted to show that this appeal to abduction is question-begging, circular, or incoherent (Fine, Laudan, van Fraassen). This paper approaches these issues by distinguishing weaker and stronger forms of abduction, and by showing how these types of inferences can be given Peircean and Bayesian probabilistic reconstructions.

The aim of my paper is to highlight that for Peirce the reality of God makes sense of the whole scientific enterprise. The belief in God is a natural product of abduction, of the "rational instinct" or educated guess of the scientist or the layman, and also the abduction of God may be understood as a "proof" of pragmatism. Moreover, I want to suggest that for Peirce scientific activity is a genuine religious enterprise, perhaps even the religious activity par excellence, and that to divorce religion from science is antithetical to both the scientific spirit and the real Peirce. Understanding the real Peirce requires to deal with his religious concerns, which are increasingly recognized as being perhaps as philosophically important as his scientific concerns. Since a key notion in this project is the idea of "il lume naturale" that Peirce borrowed from Galileo, I want also to pay attention to that expression which during years I have been following through Peirce's papers and books.

In order to try to explain some of this, my paper is arranged into four brief sections after this already long introduction: 1) God and scientific inquiry; 2) The belief in God as a product of abduction; 3) Galileo and Peirce: Il lume naturale; and by way of conclusion 4) Some remarks on the religious framework of Peirce's approach.

Abductive reasoning takes place in forming``hypotheses'''' in order to explain ``facts.'''' Thus, theconcept of abduction promises an understanding ofcreativity in science and learning. It raises,however, also a lot of problems. Some of them will bediscussed in this paper. After analyzing thedifference between induction and abduction (1), Ishall discuss Peirce''s claim that there is a ``logic''''of abduction (2). The thesis is that this claim can beunderstood, if we make a clear distinction between inferential elements and perceptive elements of abductive reasoning. For Peirce, the creative act offorming explanatory hypotheses and the emergence of``new ideas'''' belongs exclusively to the perceptive side of abduction. Thus, it is necessary to study the roleof perception in abductive reasoning (3). A furtherproblem is the question whether there is arelationship between abduction and Peirce''s concept of``theorematic reasoning'''' in mathematics (4). Both forms of reasoning could be connected, because both arebased on perception. The last problem concerns therole of instincts in explaining the success ofabductive reasoning in science, and the question whether the concept of instinct might be replaced bymethods of inquiry (5).

There are various ``classical'' arguments against abduction as a logic of discovery,especially that (1) abduction is too weak a mode of inference to be of any use, and (2) in basic formulation of abduction the hypothesisis already presupposed to be known, so it is not the way hypotheses are discovered in the first place. In this paper I argue, by bringing forth the idea of strategies,that these counter-arguments are weaker than may appear. The concept of strategies suggests, inter alia, that many inferential moves are taken into account at the same time. This is especially important in abductive reasoning, which is basically a very weak mode of inference. The importance of strategic thinking can already be seen in Charles S.Peirce's early treatments of the topic, and N.R.Hanson's later writings on abduction although they did not use the concept of``strategies.'' On the whole, I am arguing that the focus should be more on methodological processes, and not only on validity considerations, which have dominated the discussion about abduction.

It is well known that the process of scientific inquiry, according to Peirce, is drivenby three types of inference, namely abduction, deduction, and induction. What isbehind these labels is, however, not so clear. In particular, the common identificationof abduction with Inference to the Best Explanation (IBE) begs the question,since IBE appears to be covered by Peirce's concept of induction, not that of abduction.Consequently, abduction ought to be distinguished from IBE, at least on Peirce's account. The main aim of the paper, however, is to show that this distinction is most relevant with respect to current problems in philosophy of science and epistemology (like attempts to supply suitable notions of realism and truth as well as related concepts like coherence and unification). In particular, I also try to show that (and in what way) Peirce's inferential triad can function as a method that ensures both coherence and correspondence. It is in this respect that his careful distinction between abduction and induction (or IBE) ought to be heeded.