Department of Philosophy and Computational Philosophy Laboratory, Piazza Botta 6

Pavia, 27100 Italy,

and

Program in Philosophy, Science and Technology and Program in Cognitive Science

School of Public Policy and College of Computing, Georgia Institute of Technology, 685 Cherry Street

Atlanta, GA, 30332-0345 USA

An interesting and neglected point of contention about human reasoning is whether or not concrete manipulations of external objects influence the generation of hypotheses. I am focusing on the first features of what I call manipulative abduction showing how we can find in scientific and everyday reasoning methods of constructivity based on external models and action-based reasoning.

I am analyzing the problem in the light of the so-called historical-cognitive method (Nersessian, 1998). While it tries to integrate findings from research on cognition and findings from historical-epistemological research into models of actual scientific practices, assessments of the fit between cognitive findings and historical-epistemological practices aid in elaborating richer and more realistic models of cognition. There are interesting parallels that can be exploited by cognitive scientists and AI researchers, the relevance of the concept of abduction can contribute to a central issue in cognitive science: hypothesis formation both in science and in everyday reasoning.

It is well known that many reasoning conclusions that do not proceed in a deductive manner are abductive. What I call theoretical abduction (Magnani, 1999a) is, from a cognitive point of view, an internal process of reasoning. What about the "external" ways of finding hypotheses?

Many attempts have been made to model abduction by developing some formal tools in order to illustrate its computational properties and the relationships with the different forms of deductive reasoning. Some of the formal models of abductive reasoning are based on the theory of the epistemic state of an agent (Boutilier and Becher 1995), where the epistemic state of an individual is modeled as a consistent set of beliefs that can change by expansion and contraction (belief revision framework). This kind of sentential frameworks exclusively deals with selective abduction (diagnostic reasoning) and relates to the idea of preserving consistency. If we want to provide a suitable framework for analyzing the most interesting cases of conceptual changes in science we do not have to limit ourselves to the sentential view of theoretical abduction but we have to consider a broader inferential one which encompasses both sentential and what I call model-based sides of creative abduction.

If we want to deal with the nomological and most interesting creative aspects of abduction (Magnani 1999a) we are first of all compelled to consider the whole field of the growth of scientific knowledge. Related to the high-level types of scientific conceptual change (Thagard 1992) are different varieties of model-based abductions (see, for examples, Magnani 1999b). Following Nersessian (1999), I use the term "model-based reasoning" to indicate the construction and manipulation of various kinds of representations, not necessarily sentential and/or formal. Obvious examples of model-based reasoning are constructing and manipulating visual representations, thought experiment, analogical reasoning, but also the so-called "tunnel effect" (Cornuéjols et al. 2000), occurring when models are built at the intersection of some operational interpretation domain – with its interpretation capabilities – and a new ill-known domain.

What exactly is model-based abduction from a philosophical point of view? Peirce stated that all thinking is in signs, and signs can be icons, indices, or symbols. Moreover, all inference is a form of sign activity, where the word sign includes "feeling, image, conception, and other representation" (CP 5.283), and, in Kantian words, all synthetic forms of cognition. That is, a great part of the thinking activity is model-based. Of course model-based reasoning acquires its peculiar creative relevance when embedded in abductive processes.

For Peirce a Kantian keyword is synthesis, where the intellect constitutes in its forms and in a harmonic way all the material delivered by the senses. Surely Kant did not consider synthesis as a form of inference but, notwithstanding the obvious differences, I think synthesis can be related to the Peircian concept of inference, and, consequently, of abduction. After all, when describing the ways the intellect follows to unify and constitute phenomena through imagination Kant itself makes use of the term rule (Kant 1929, A140, B179-180, 182), and also of the term procedure (Kant 1929, A140-B179-180, 182). We know that rules and procedures represent the central features of the modern concept of inference.

Most of these forms of constitution of phenomena are creative and, moreover, characterized in a model-based way. Let me show some examples of model-based inferences. It is well known the importance Peirce ascribed to diagrammatic thinking, as shown by his discovery of the powerful system of predicate logic based on diagrams or "existential graphs". As we have already stressed, Peirce considers inferential any cognitive activity whatever, not only conscious abstract thought; he also includes perceptual knowledge and subconscious cognitive activity. For instance in subconscious mental activities visual representations play an immediate role.

Peirce gives an interesting example of model-based abduction related to sense activity: "A man can distinguish different textures of cloth by feeling: but not immediately, for he requires to move fingers over the cloth, which shows that he is obliged to compare sensations of one instant with those of another" (CP 5.221); this idea surely suggests that abductive movements also have interesting extra-theoretical characteristics and that there is a role in abductive reasoning for various kinds of manipulations of external objects (cf. below, the problem of "action-based, manipulative abduction"). One more example is given by the fact that the perception of tone arises from the activity of the mind only after having noted the rapidity of the vibrations of the sound waves, but the possibility of individuating a tone happens only after having heard several of the sound impulses and after having judged their frequency. Consequently the sensation of pitch is made possible by previous experiences and cognitions stored in memory, so that one oscillation of the air would not produce a tone.

To conclude, all knowing is inferring and inferring is not instantaneous, it happens in a process that needs an activity of comparisons involving many kinds of models in a more or less considerable lapse of time. All sensations or perceptions participate in the nature of a unifying hypothesis, that is, in abduction, in the case of emotions too: "Thus the various sounds made by the instruments of the orchestra strike upon the ear, and the result is a peculiar musical emotion, quite distinct from the sounds themselves. This emotion is essentially the same thing as a hypothetic inference, and every hypothetic inference involved the formation of such an emotion" (CP 2.643).

What happens when the abductive reasoning in science is strongly related to extra-theoretical actions and manipulations of "external" ojects? When abduction is "action-based" on external models?. When thinking is "through doing" as illustrated in the simple case above of distinguishing the simple textures of cloth by feeling? To answer these questions I will delineate the first features of what I call manipulative abduction by showing how we can find in scientific and everyday reasoning methods of constructivity based on external models and actions.

Manipulative abduction happens when we are thinking through doing and not only, in a pragmatic sense, about doing. It refers to an extra-theoretical behavior that aims at creating communicable accounts of new experiences to integrate them into previously existing systems of experimental and linguistic (theoretical) practices. Gooding (1990) refers to this kind of concrete manipulative reasoning when he illustrates the role in science of the so-called "construals" that embody tacit inferences in procedures that are often apparatus and machine based. The embodiment is of course an expert manipulation of objects in a highly constrained experimental environment, and is directed by abductive movements that imply the strategic application of old and new templates of behavior mainly connected with extra-theoretical components, for instance emotional, esthetical, ethical, and economic.

The hypothetical character of construals is clear: they can be developed to examine further chances, or discarded, they are provisional creative organization of experience and some of them become in their turn hypothetical interpretations of experience, that is more theory-oriented, their reference is gradually stabilized in terms of established observational practices. Step by step the new interpretation - that at the beginning is completely "practice-laden" - relates to more "theoretical" modes of understanding (narrative, visual, diagrammatic, symbolic, conceptual, simulative), closer to the constructive effects of theoretical abduction. When the reference is stabilized the effects of incommensurability with other stabilized observations can become evident. But it is just the construal of certain phenomena that can be shared by the sustainers of rival theories. Gooding (1990) shows how Davy and Faraday could see the same attractive and repulsive actions at work in the phenomena they respectively produced; their discourse and practice as to the role of their construals of phenomena clearly demonstrate they did not inhabit different, incommensurable worlds in some cases. Moreover, the experience is constructed, reconstructed, and distributed across a social network of negotiations among the different scientists by means of construals.

To illustrate this process - from manipulations, to narratives, to possible theoretical models (visual, diagrammatic, symbolic, mathematical) - I have considered (Magnani, 2000b) some observational techniques and representations made by Faraday, Davy, and Biot concerning Oersted’s experiment about electromagnetism. They were able to create consensus because of their conjectural representations that enabled them to resolve phenomena into stable perceptual experiences. Some of these narratives are very interesting.

Recent research, taking an ecological approach to the analysis and design of human-machine systems, has shown how expert performers use action in everyday life to create an external model of task dynamics that can be used in lieu of an internal model (Kirlik, 1998). Not only a way for moving the world to desirable states, action performs an epistemic and not merely performatory role that is very relevant to abductive reasoning.

The whole activity of manipulation is devoted to build various external epistemic mediators that function as an enormous new source of information and knowledge. I derive this expression from the cognitive anthropologist Hutchins (1995), that coins the expression "mediating structure" to refer to various external tools that can be built to cognitively help the activity of navigating in modern but also in "primitive" settings. Any written procedure is a simple example of a cognitive "mediating structure" with possible cognitive aims: "Language, cultural knowledge, mental models, arithmetic procedures, and rules of logic are all mediating structures too. So are traffic lights, supermarkets layouts, and the contexts we arrange for one another’s behavior. Mediating structures can be embodied in artifacts, in ideas, in systems of social interactions […]" (290-291).

In this light manipulative abduction in science represents a kind of redistribution of the epistemic and cognitive effort to manage objects and information that cannot be immediately represented or found internally (for example exploiting the resources of visual imagery).

Already in the Dialogues Concerning the Two Chief World Systems (1632), accentuating the role of observational manipulations Galileo presents an anatomist that, manipulating a cadaver, is able to get new, not speculative, information that goes beyond the "world of paper" of the Peripatetic philosophy. It is well known that recent philosophy of science has paid a great attention to the so-called theory-ladenness of scientific facts (Hanson, Popper, Kuhn). Nevertheless a lot of new information in science is reached by observations and experiments, and experiments are the fruit of various kinds of artifactual manipulations: the different strategies correspond to the expert manipulations of objects in a highly constrained experimental environment, directed by abductive movements that imply the application of old and new extra-theoretical templates of behavior.

With Galileo’s achievements, we observe that human "scientific" thinking is related to the manipulation of a material and experimental environment that is no longer natural. Knowledge is finally seen as something cognitively distributed across scientists, their internal "minds", and external artifacts and instruments. Experiments and instruments embody in their turn external crystallization of knowledge and practice. Modern science is made by this interplay of internal and external. An immediate consequence of Galileo’s ideas is the critique of the authority, that advocated the knowledge relevance of a "world of paper", mainly internal from the cognitive point of view. Gooding observes: "It is ironical that while many philosophers admire science because it is empirical as well as rational, philosophical practice confines it to the literary view that Galileo rejected" (1990, xii). Galileo’s "book of nature" and his systematic use of the telescope are the revolutionary epistemic mediators that characterize the cognitive power of the new way of producing intelligibility.

We still know very little about what governs the action-based abduction. I plan to better delineating some of the manipulative templates of behavior that are active in creative abduction comparing scientific and everyday reasoning: 1. action elaborates a simplification of the reasoning task and a redistribution of effort across time when we "need to manipulate concrete things in order to understand structures which are otherwise too abstract" (Piaget 1974), or when we are in presence of redundant and unmanageable information; 2. action can be useful in presence of incomplete or inconsistent information - not only from the "perceptual" point of view - or of a diminished capacity to act upon the world: it is used to get more data to restore coherence and to improve deficient knowledge; 3. action as a control of sense data illustrates how we can change the position of our body (and/or of the external objects) and how to exploit various kinds of prostheses (Galileo’s telescope, technological instruments and interfaces) to get various new kinds of stimulation: action provides some tactile and visual information (e. g., in surgery), otherwise unavailable; 4. action enables us to build external artifactual models of task mechanisms instead of the corresponding internal ones, that are adequate to adapt the environment to agent’s needs: experimental manipulations exploit artificial apparatus to free new possible stable and repeatable sources of information about hidden knowledge and constraints; 5. in science experimental action shows a sensibility to the aspects of the phenomenon which can be regarded as curious or anomalous; manipulations have to be able to introduce potential inconsistencies in the received knowledge (Oersted’s report of his well-known experiment about electromagnetism is devoted to describe some anomalous aspects that did not depend on any particular theory of the nature of electricity and magnetism; 6. action exhibits a preliminary sensibility to the dynamical character of the phenomenon, and not to entities and their properties, common aim of manipulations is to practically reorder the dynamic sequence of events in a static spatial one that should promote a subsequent bird’s-eye view (narrative or visual-diagrammatic).