Friday, March 28, 2008


The aim of post is threefold: first to clarify the concept abduction by showing how it is differentiated from induction and hypothesis. Second to show how abduction is related in Peirce’s philosophical system, especially to the understanding of ‘precepts’ and ‘perceptual judgments’. Thirdly to summarise Peirce’s ideas on abduction as an instinct for guessing. Finally I will critique Peirce’s notion of abduction from the perspective of embodied cognition.



The first point to consider when trying to clarify abduction, induction and hypothesis is the problems caused by Peirce’s habit at different stages of his life of assigning different neologisms to represent similar ideas. Abduction is no exception since it also went by the name of ‘retroduction’ and even ‘hypothesis’. It is important to make clear that differently named terms in Peirce’s system are not necessarily conceptually synonymous, see for example the forceful argument of Deledalle (2000) makes regarding how Peirce’s thought was subject to radical change in his lifetime. There really daunting implication of this is because of the fragmentary nature of Peirce’s writings, and because he published no canonical exposition of his philosophical system in his lifetime, the researcher who is primary interested applying Peirce’s thought has to become a Peircean scholar in order to navigate the minefield of misinterpretation and confusion.


The second problem, as already intimated, pertains especially to Peirce’s use of the term hypothesis. For hypothesis is often used, not just as a synonym for abduction, but also in the sense of its traditional meaning as defined in the Cambridge Dictionary of Philosophy for example as, “A hunch, speculation or conjecture proposed as a possible solution to a problem” (Honderich 1995, 385).

In this sense, an hypothesis is common to both modes of logical inference deduction and induction, the function of the hypothesis is to provide a claim that is tested in induction and, if found to be robust, applied in deduction. Peirce’s innovation was that he added a third mode of logical inference – abduction. Like induction and deduction, abduction involves a hypothesis, however, unlike them, the abductive inference does not begin with a hypothesis as its starting point, but rather it produces one as its end result.

I want to examine this last claim in more detail since it clarifies the confusion between hypothesis and abduction. The following quotation from Peirce explains the relationship between deduction, induction and abuction:

Deduction is the only necessary reasoning... It starts from a hypothesis, the truth or falsity of which has nothing to do with the reasoning; and of course its conclusions are equally ideal….Induction is the experimental testing of a theory. The justification of it is that, although the conclusion at any stage of the investigation may be more or less erroneous, yet the further application of the same method must correct the error….. Abduction consists in studying facts and devising a theory to explain them. Its only justification is that if we are ever to understand things at all, it must be in that way" (Peirce 1998, 205).

One of the unfortunate consequences of the concept of Abduction successfully entering the academic mainstream is that seemingly canonical definitions proliferate, but when they are examined they all differ in some important respects . Vagueness emerges especially in regards to an inappropriate emphasis on the principles rather than the process of forming an abductive inference. An example of this is the definition in The Oxford Companion to Philosophy which is quoted here in its entirety:

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" (Honderich 1995).

The problem with this definition is that it does not demarcate with sufficient clarity the difference between ‘an inductive hypothesis’ and ‘an abductive hypothesis’. With the result that it becomes easy to conceive of abduction merely a species of induction. One of the reasons the confusion surrounding the terms is so prevalent is that even Peirce himself was guilty of convoluted abduction with hypothesis, he wrote, “in almost everything I printed before the beginning of [the twentieth] century I more or less mixed up [abduction] and induction . . .” (CP 8.227).

Thomas Sebeok (1981) highlights this problem of hypothesis being common to both induction and abduction. He claims that hypothesis is conceived of by logicians as “an overly “narrow and formalistic conception of inference as necessarily having formulated judgments from its premises" (33). However, with abduction no judgement can be formulated in this way because no premises exist in an abduction: all the inquirer has to work with is a set of seemingly unrelated facts.


In order to differentiate between the two kinds of hypothesis, Sebeok says that the analysis needs to be processes led rather than definition led. Process led means that it should focus especially on the chronology of the various hypothetical and perceptual steps which lead to either an induction or an abduction. The simple rule to apply here is, induction seeks some facts to prove its hypothesis, whist abduction seeks an hypothesis to explain its facts (Sebeok 1981 34).

In induction a person approaches the facts already armed with a theory to explain them. This inductive hypothesis may be ephemeral. Indeed ephemerally is arguably a characteristic common to all hypotheses. But in induction the hypothesis nevertheless should be strong enough to determine which facts are relevant and which are irrelevant - and consequently also suggest to the inquirer how the process of induction should then proceed. In abduction, however, the confidence is lower because the ordering of theory and facts is reversed. A person begins with a number of seemingly unrelated facts. But armed with the feeling that they may be related somehow (CP 7.218). Peirce notes that the abductive inference often comes in a flash of inspiration, which he calls an act of insight, but of an extremely fallible kind. While it may be true that all the different elements of the hypothesis are already present in a person’s mind before making the abduction, the idea of putting them together is what flashes the new suggestion before the person's contemplation (CP 5.181).

In summary, the way to differentiate adduction from induction is to realise that there must first be an abduction for an induction to take place. Simply stated, the difference between abduction and induction is that abduction produces the hypothesis while induction tests the hypothesis.

It is impossible to see this is one does not take a process-led approach, for when induction and abduction are presented as principles, the two stages of inference formation are easily collapsed into one overarching concept – the hypothesis. This is why in the scientific method pioneered by Galileo and Bacon, the abductive stage of hypothesis formation is simply collapsed into induction. In the twentieth century this collapse was ironically reinforced by Karl Popper's explication of the hypotheco-deductive method. Popper considers the hypothesis is considered to be just “a guess” (Popper 2002, 536), however, in terms of the chronology of the process, this guess is already the starting point for the testing of the facts in an induction, rather than an awareness of a possible connection between them that will produce a flash of insight characteristic of an abduction.


Another way abduction and induction can be distinguished is the strength of inferences which lead from them. An example of this is found in Sebeok (1981, 34). Imagine a crime has been committed. Detectives working on the case discover a vital clue when a torn piece of paper comes to light, containing a specimen of handwriting from an anonymous source. The identity of the author is suspected and his desk, to which only he has access, is thoroughly searched. In the desk a notebook is found, in which one of the pages has been torn out and whose torn edges exactly match that of the paper in question. Sebeok argues that it is a fair hypothesis to infer the owner of the desk is the author of the writing. But, if the hypothesis were taken an induction, then he argues inference could never be justified with this degree of certainty. For the only permitted conclusion that induction allows a person to make is that the two matching torn pieces of paper might suggest a rule by which other torn pieces of paper can be compared in future. Whereas in abduction it is the nature of the inference presumes the two edges are same because they seem to exactly match. (Sebeok 1981, 34). This seems contradictory until it is realised that the purpose of logic is to formulate general principles from particular insights. In this example, although the insight is dramatic and strong, it could only apply to the particular circumstances in which it occurred, thus it is a poor hypothesis for induction. Peirce warns that this apparent certainty is not the basis for ontological security but rather it is precisely what makes abduction a bolder and more perilous step (CP 2.632).

This once more underscores the point that the notion of 'hypothetic inference' found in both abduction and induction (and indeed in deduction as well) it is not the same inference in every case.


The second part of this post outlines theoretically how an abduction is arrived at by examining the relationship between abduction and two other Peircean concepts: percepts, and perceptual judgements. The concepts of Percept and perceptual judgements will be explained in the paragraphs to follow, but it is useful at this stage to familiarise the reader with the structure of the steps that will combine to produce an abductive inference, even though the steps themselves are undefined at this stage. These steps are three: the percept acts as the ground for the perceptual judgement which acts as the ground the abductive inference.


The percept can be defined as the direct object of all thought. In this sense it exists in a state Peirce calls Firstness, which is notoriously difficult to explain, because firstness does not refer to anything else, nor does it lie behind anything. The first is that which simply is of itself (CP 1. 356). If the analogy is helpful, a percept can be likened to a “thought-image”, but with the caveat that this image is only taken to mean product of a person’s direct perception, rather than being a representation (CP 4.539). Percepts are not representations as such, because they are produced by mental processes we are not directly aware of, that happen below the threshold of conscious awareness (7.624 ). This means that the percept is not capable of describing itself; for such a description would involve analysis. However this does not mean that once a person has a percept, they may not then contemplate it, and say to themselves, “That appears to be a yellow chair” for example. In which case in ordinary language it might be presumed that the chair of the previous example is perceived to be yellow. However this conclusion is erroneous, because the sentence, “the chair is yellow” contains a judgment about the chair, which because it is a judgement involves processes of conscious thought (7.626 ).


It is this judgement that Peirce calls ‘the perceptual judgment.’ A Perceptual judgment can be defined as, a proposition of existence determined by the percept, which it interprets. (4.539 fn) Such a judgment takes place in an act of forming a mental proposition and then assenting to that proposition, in the sense of professing to one’s future self what the character of the present percept shall be (5.115; 7.631).

Perceptual judgments are the first building block of knowledge. They appear to exist in what Peirce calls Secondness. Secondness consists in one thing acting upon another, -- [a] brute action (CP 8.330). Perceptual judgements impress themselves on the mind in this way. They have the characteristic of being “necessarily veracious in greater or less degree according to the effort made” (5.141). But just because they are veracious it does also mean that they are true. The reason for this is found when the relationship between percepts and perceptual judgements is explored more fully.

As I have mentioned, percepts cannot be subject to conscious discriminations because they are apprehended below the threshold of consciousness. They are for that reason neither true, nor false, they just are. Similarly, there is not enough information in a perceptual judgement to confirm of deny the percept. For instance one may be mistaken about one’s perceptual judgement that the chair is yellow, but all this means is that further contemplation of the chair yields a different percept which in turn yields a different perceptual judgement the particular veracity of which is no different to the first, but is felt to be contradicted only by linking the two judgements together in an action of mediation. That kind of judgement in which one could say which perceptual judgements is true and which is false can only be reached when a number of perceptual judgements are compared and evaluated. To clarify this point Peirce provides the following example:

I may judge that I see a clean white surface. But a moment later I may question whether the surface really was clean, and may look again more sharply. If this second more veracious judgment still asserts that I see a clean surface, the theory of the facts will be simpler than if, at my second look, I discern that the surface is soiled. Still, even in this last case, I have no right to say that my first percept was that of a soiled surface. I absolutely have no testimony concerning it, except my perceptual judgment, and although that was careless and had no high degree of veracity, still I have to accept the only evidence in my possession (5.141).
Another important characteristic of perceptual judgements is that, although they are of themselves strikingly singular in nature, the fact that they are judgements means that they also involve generality to some degree. Although at first glance this seems surprising: it seems counter intuitive that anything so immediate as a perceptual judgement could contain any generality at all. However if the term ‘general’ is defined in the Aristotelian sense of “being that which is fitted by nature to be predicated of many things”, then it must be recognized that every judgments contains an element of generality, because it identifies a percept with a quality, and a quality is a general, thus perceptual judgements involve generality in their predicate (5.151).


The human mind’s further consideration of percepts and perceptual judgments is the basis upon which abductions are reached. Armed with this information we can make a more precise definition of abduction. It is the evaluation a person makes to assess different perceptual judgements of seemingly equal veracity. This is where the element of mediation enters into the analysis, "to subject these processes to logical analysis is simply to arrive at the logic of an abductive inference" (CP 5.181).

To exemplify the process behind this idea consider the following quotation from Peirce:

Looking out my window this lovely spring morning I see an azalea in full bloom. No, no! I do not see that; though that is the only way I can describe what I see. That is a proposition, a sentence, a fact; but what I perceive is not proposition, sentence, fact, but only an image, which I make intelligible in part by means of a statement of fact. This statement is abstract; but what I see is concrete. I perform an abduction when I so much as express in a sentence anything I see. The truth is that the whole fabric of our knowledge is one matted felt of pure hypothesis confirmed and refined by induction. Not the smallest advance can be made in knowledge beyond the stage of vacant staring, without making an abduction at every step (Sebeok 1981, 20) [Ms. 692].


The above quotation pushes to the fore the most perilous aspect of abduction, for it is merely guessing. But Peirce was struck by the frequency that people guess right about things, which was far greater than would be presupposed by mere chance (CP 8.238). For example in the sciences:

Think of what trillions of trillions of hypotheses might be made of which one only is true; and yet after two or three or at the very most a dozen guesses, the physicist hits pretty nearly on the correct hypothesis…. Even now he cannot give any exact reason for his best guesses. It appears to me that the cleanest statement we can make of the logical situation…is to say that man has a certain Insight, not strong enough to be oftener right than wrong, but strong enough not to be overwhelmingly more often wrong than right. An insight, I call it, because it is to be referred to the same general class of operations to which perceptive judgments belong." This faculty is at the same time of the general nature of Instinct, resembling (Peirce 1998, 217).
Peirce maintained elsewhere that the ability of a newly hatched chick to pick up food, [is] like abductive inference," and can be further traced back to the “animal instincts for, respectively, getting food and reproduction” (Ms. 692, quoted in Sebeok 1981, 20).

Peirce considers abduction as resting upon the hope that there is sufficient affinity between the reasoner's mind and nature to render guessing not altogether hopeless, provided, he adds that, each guess is checked by comparison with observation" (CP 1.121).

That no new truth can come from induction or from deduction, we have seen. It can only come from abduction; and abduction is, after all, nothing but guessing. We are therefore bound to hope that, although the possible explanations of our facts may be strictly innumerable, yet our mind will be able in some finite number of guesses, to guess the sole true explanation of them. That we are bound to assume, independently of any evidence that it is true (Peirce 1998, 107).


The way that abduction relates to percepts and perceptual judgements can be criticised because of its complexity and unwieldiness. This I argue is due to Peirce trying to explain these concepts using a representational framework to describe something that is in essence not representational. The processes of judging percepts happens below a level of conscious understanding. This may be explained in the way Peirce has explained it, but the explanation implies too forcefully a process of conscious analysis, whereas it is in fact only an interpretation of what presumably goes on in the mind. Another way to articulate these preconscious processes is from the perspective of embodied cognition theory; what may be called the logic of simulation. This logic ironically owes a dept to Peirce, because it is based heavily of pragmatism. Here is a sketched account of this position taken from the work of Adenzato & Garbarini (2006).


A pragmatic dimension of the theory of knowledge has emerged from the present interdisciplinary analysis of the as if concept—an analysis involving the neurosciences, cognitive sciences, anthropology and ethnology. This pragmatic dimension underscores the role of action, and especially simulation and interaction, in the knowing process.

The embodied cognition perspective views the mind no longer as a set of logical/abstract functions, but as a biological system, which is rooted in body experience and interwoven with action and interaction with other individuals. Specifically acting in the world, interacting with the objects and individuals in it, representing the world, perceiving it, categorizing it and understanding its meaning are merely different levels of the same relationship that exists between an organism and its environment. For example, we might ask, ‘how do children manage to become expert walkers?’ An embodied cognition answer contends it is not due to the mere application of previous (genetically codified) instructions, but, rather, due to behaviour emerging out of the continuous interaction among neural, bodily and environmental factors.

Embodied cognition allows not only for the planning and execution of actions, but for their representation as well. Based on a principle of cognitive economy, the same mechanism that leads to the explicit execution of an action also allows for its representation (and for the representation of its underlying objects) when the action is only virtually activated. Hence, representing objects and actions implies a simulative process, an implicit as if action.

Recent discoveries in the neurophysiological domain have experimentally confirmed the existence of a mechanism by which an object’s shape and function are coupled and perceived directly by an observer. In a series of studies Rizzolatti and colleagues (Rizzolatti & Craighero, 2004) have discovered the existence of groups of neurons in the premotor cortex of monkeys and humans, which fire when specific actions are executed. Some are triggered by the mere observation of an object, while other called mirror neurons are triggered by observing another person executing that action with the object. The activity of these neurons can be conceptually captured by referring to a simulation mechanism in the sense that when an object is under observation, a motor schema appropriate to the characteristics of that object is activated as if the observer were interacting with it.

Similarly, when observing another individual executing an action with an object, the observer’s neural system is activated as if he himself were executing the same action. In both instances, motor activation is only virtual - the action is not actually carried out, but it is neurally simulated.

This perspective makes it possible to maintain a representational conception of the mind, without adopting the model of abstract representations of formal logic and the linguistic/propositional format in which they are expressed. People construct representations of their world based not on theoretical categories, as traditionally assumed, but on pragmatic categories, derived from the dynamic interaction of living organisms with their adaptive environments.

I believe that if a strict representational framework should be abandoned when the discussion turns to percepts and perceptual judgements and especially in respect of his semi-mystical formulation of an instinct for guessing. Instead an as if schemata/simulation frame work should be adopted, because this leads to a clearer picture of the function of abduction, which can be conceived of as a bridge between preconscious activity and the conscious reporting of that activity. By viewing abduction from the perspective of as if schema, it is possible to delineate the concept with more precision that Peirce could achieve. The feeling which is the basis of an abduction is in fact the result of cognition taking place below a threshold of conscious reporting. Not as Peirce asserted due to direct perception of representations. Abduction is therefore the flash of insight where a hitherto non conscious thought announces itself to consciousness.

Peirce is made an important if overlooked contribution to the understanding and development of the logic of representation, but his work was also an important precursor of the logic of simulation as well. Not only did he perceive the limits of analytical thought in respect of his critique of novelty, but his understanding of logic was so sophisticated that all the major tenants of simulation are recognisable in his descriptions, even though they are framed in terms which fight to mislead the inquirer at every step. It is as if a medieval alchemist works were found to contain all the laws governing modern chemistry, but written in a language best suited to discussion of the transmutation of base metals into gold.


Adenzato, Mauro and Francesca Garbarini (2006) “The As If in Cognitive Science, Neuroscience and Anthropology: A Journey Among Robots, Blacksmiths And Neurons”

Deledalle, GĂ©rard (2000) Charles S. Peirce's Philosophy of Signs - Essays in Comparative Semiotics, Bloomington USA: Indiana University Press

Flach, Peter & Antonis Kakas (editors), (2000) Abduction and Induction: essays on their relation and integration, Norwell, Mass, US: Kluwer Academic Publishers.

Honderich, Ted (editor), (1995): The Oxford Companion to Philosophy, Oxford, UK: Oxford University Press.

Peirce, Charles Sanders (1998): The Essential Peirce: Selected Philosophical Writings, Vol. 2 (1893-1913), edited by the Peirce Education Project, Bloomington, US: Indiana University Press
___________________ (1931-1935): The Collected Papers of Charles Sanders Peirce, Vols. I-VI, edited by Charles Hartshorne and Paul Weiss, Cambridge, US: Harvard University Press.
___________________(1958): The Collected Papers of Charles Sanders Peirce, Vols. VII-VIII, Edited by AW Burks, Cambridge, US: Harvard University Press

Popper, Karl (2002) Conjectures and Refutations: The Growth of Scientific Knowledge, London, UK: Routledge.

Rizzolatti, G., & Craighero, L. (2004). The mirror-neuron system. Annual Review of
Neuroscience, 27, 169–192.

Sebeok, Thomas with Jean Umiker Sebeok (1981): "You Know My Method" in The Play of Musement, Bloomington, Indiana USA: Indiana University Press


Heresiarch said...

If you are interested in Hartshorne, applied cosmologically -- with a dose of Whitehead's "philosophy of organism"--the stop by the refeshment stand at

Notebooks said...
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