ABDUCTION, PRAGMATISM, AND THE SCIENTIFIC IMAGINATION

H.G. Callaway

Peirce claims in his Lectures on Pragmatism [CP 5.196] that “If you carefully consider the

question of pragmatism you will see that it is nothing else than the question of the logic of

abduction;” and further “no effect of pragmatism which is consequent upon its effect on

abduction can go to show that pragmatism is anything more than a doctrine concerning the logic

of abduction.” Plausibly, there is, at best, a quasi-logic of abduction, which properly issues in

our best means for the methodological evaluation and ordering of (yet untested) hypotheses or

theories. There is always a range of explanatory innovations that may be proposed, from more

conservative to less conservative; and it is important, in light of what Peirce has to say on the

relation of abduction to pragmatism, that in ruling out “wild guessing,” attention be initially

directed to more conservative proposals. Still conservativism, which we might understand in

terms of Peircean continuity, is sometimes justly sacrificed for greater comprehension or overall

simplicity of approach. This paper explores the relationships among Peircean abduction and

pragmatism, the “theoretical virtues” approach to the evaluation of hypotheses, and contextual

constraint on the scientific imagination.

1. Background for Peircean Abduction

An element of the historical background of Peirce on abduction can plausibly be traced to the

Coleridge-Emersonian contrast between “imagination” and “fancy,” which explicates or

This paper was presented at the Applying Peirce Conference, Helsinki, Finland, June 2007, at the Conference of the Italian Society for Logic and Philosophy of Science, Milan, Italy October, 2007, and at a conference of the Wesleyan Philosophical Society, Durham, NC, March 2008. I want to especially thank Carlo Rovelli for his thoughtful and appreciative comments at the meeting in Milan.

sharpens the ordinary usage and dictionary definition of the English word “imagination.”

Emerson contrasts imagination and fancy vividly in his Letters and Social Aims (1875):

Imagination is central; fancy superficial. Fancy relates to surface, in which a great part of life lies. The

lover is rightly said to fancy the hair, eyes, complexion of the maid. Fancy is a willful imagination, a

spontaneous act; fancy, a play as with dolls and puppets which we chose to call men and women;

imagination, a perception and affirming of a real relation between a thought and some material fact. Fancy

amuses; imagination expands and exalts us. Imagination uses an organic classification. Fancy joins by

accidental resemblance, surprises and amuses the idle, but is silent in the presence of great passion and

action. Fancy aggregates; imagination animates. Fancy is related to color; imagination to form. Fancy

paints; imagination sculptures.1

In effect, flights of fancy are contrasted with the constructive, cognitively oriented imagina-

tion. “Imagination is central,” says Emerson, while “fancy is a willful imagination” and

sometimes “a play as with dolls and puppets which we chose to call men and women.” Imagi-

nation, in contrast, always relates thought to “some material fact,” it is “a perception,”

according to Emerson, a matter of at least taking something to be true, since we do not affirm

the perception that so and so, and at the same time call it an illusion, too. “Imagination uses an

organic classification,” says Emerson, while fancy “joins by accidental resemblances” and “is

silent in the presence of action.” From a philosophical perspective, as contrasted with that of

literature as purely aesthetic interest, Emerson’s fully developed conception of imagination is

a refinement of the common-sense notion which eliminates or sharply separates the element

of willful fantasy, and it is a significant precursor of C.S. Peirce on abduction. The point is

connected with what I have called Emerson’s anti-nominalism.

Emerson stresses the claim that thought, as cognitive accomplishment, makes us free, partly

by extending human control over nature; and, he equally emphasizes normative observation of

laws of thought. “For,” he says, “thought “ too must act according to eternal laws, and all that is

willful and fantastic in it is in opposition to its fundamental essence.”2 From this one may safely

1 . R.W. Emerson 1875, “Poetry and Imagination,” in Letters and Social Aims. (Boston: Osgood). To understand something of Emerson’s development from Coleridge, compare Coleridge 1817, Biographia Literaria, Chapter 4.

2 . R.W. Emerson 1860, in Callaway, H.G. ed. 2006, Ralph Waldo Emerson: The Conduct of Life, A Philosophical Reading. (Lanham, MD: University Press of America), p. 11.

2

infer, that the “organic classification” which imagination is to employ corresponds to those

concepts required for and identified in ascertained law of nature, including, in Emerson, natural

moral laws. So long as we are subject to stubborn circumstance, and have some need to expand

our freedom and power, there is always a prospective “higher law,” which we have yet to

observe, recognize, or institute. It is this kind of point which made of Emerson both a student of

the sciences and an abolitionist.

Central to Peircean abduction is the idea that we need some deeper understanding of the

origin of reasonable hypotheses, or educated guesswork,3 in contrast with wild or fantastic

guessing, and equally, we have need for comparative evaluation of hypotheses at a point short of

their confirmation or refutation by reference to predictions. Peirce proposed to investigate the

logic of abduction, though to hold that there is a logic of abduction makes a strong claim on

Peircean instinct, existing knowledge, or accepted theory to guide the evaluation of new

hypotheses. Peirce claimed, in a very suggestive formulation, that the question of pragmatism is

the question of abduction, and the claim is of special interest for our studies of American

philosophy, if we are concerned to resist the tendency of the current revival of pragmatism to

reduce to a polite, anti-intellectualism of pleasing conversation or a “vulgar pragmatism” of the

predominance of the numbers of voices or of institutional rigidities. For Peirce, the relation of

pragmatism to abduction turns on the question of the conceivable practical effects of an

hypothesis. Once confirmed and established by scientific inquiry, it is clear that our erstwhile

hypothesis may indeed embody practical effects. Yet the more interesting question is to see how

consideration of conceivable methodological consequences of alternative hypotheses may help

direct attention among them, prior to confirmation or disconfirmation of competing predictions.

We want to understand how accepted laws or generalizations and concepts of a given field of

inquiry may structure and constrain the formation and initial plausibility of new hypotheses in

3 . “In a word, hypothesis is guesswork,” say Quine and Ullian 1978, in The Web of Belief (second ed. New York: Random House), p. 65, “but it can be enlightened guesswork.” One may doubt that even enlightened guesswork amounts to a logic of abduction.

3

answer to outstanding problems of the field. The question of pragmatism is the question of

abduction, wrote Charles Sanders Peirce, and I modify this here to say that one question of

pragmatism is the question of the reasonability of evaluating (untested) hypothesis by reference

to the range of scientific theory and results which we seek to correct or modify: there being

“better and worse” among untested hypotheses.

The point stands in some tension with William James’s dictum that “on pragmatic principles

we cannot reject any hypothesis if consequences useful to life flow from it.”4 This Jamesian

dictum finds at least this much support in Peirce’s Lectures on Pragmatism, where he wrote

that “if pragmatism is the doctrine that every conception is a conception of conceivable

practical effects, it makes conception reach far beyond the practical. It allows any flight of

imagination, provided this imagination ultimately alights upon a possible practical effect; and

thus many hypotheses may seem at first glance to be excluded by the pragmatical maxim that

are not really so excluded.”5 Arguably, Peirce means to include hypotheses not of a narrow

practical sort, while James aims to include comforting non-empirical generalizations. We

expect that is, in spite of the similar formulations, that for James and Peirce, the range of “live

options” will differ.

The theme of a better and worse to untested hypotheses elaborates meliorism regarding the

growth of knowledge. Viewing methodology as guiding the practice of inquiry and science, we

naturally view initial evaluation of hypotheses as part of this practice. Many remain skeptical of

Peirce’s conception of truth as the opinion fated to be accepted at the end of inquiry. No

particular statements are ultimately fated to be accepted independent of our practice and our

choice of methods. But putting that question aside, and understanding the meaning of accepted

doctrine in terms of conceivable practical effects, if the question of pragmatism is the question of

abduction, then pragmatism requires that accepted scientific doctrine have some tendency, a

propensity in some degree, to expand and transform into a fuller account—in the direction of

4. William James 1907, Pragmatism, p. 105. 5. Peirce 1903, CP 5.196.

4

truth. For we expect that our new hypothesis will have significant explanatory and predictive

power, not in isolation, but only as logically combined with the body of knowledge which it

would be used to modify.

2. Scientific Meliorism and Popper’s “Bold Conjectures”

The topic of abduction is not one always well beloved by empiricist. Abduction is one area of

Peirce’s thought were the charge of “psychologism” and/or subjectivism seems to regularly arise.

Most often this presupposes, in the philosophy of science at least, a stronger version of the

distinction between the “context of discovery” and the “context of justification.” The argument

may be made that it makes no difference how we come by our hypotheses—which I doubt—,

what matters is only whether or not we can assemble sufficient evidence. From that perspective,

the idea of a “logic of abduction” has little appeal, and one simply substitutes talk of, say,

“educated guesswork.” In contrast, I will argue for an objective basis for reasoned preferences

among untested hypotheses, and emphasize that even on a diminished basis, if there is strictly no

logic of abduction, still we need some account of the difference between reasonable hypothesis

and wild guessing.

It seems obvious that not just any hypothesis will be as good as any other in the context of a

particular scientific report. Instead, an eligible hypothesis must be strongly relevant to the results

reported and have a clear connection to the subject-matter and the particular problems addressed

in prior sections of the paper. We expect, too, that there will be some strong relevancy to the

methods employed, or usually employed, in the investigation of similar problems. Lastly, the

suggested hypothesis would have to make some plausible contribution to the possible

interpretation of the results reported in the paper. The suggestion of possible further hypotheses

belongs in the “Discussion” section of a scientific paper, because it indicates something of the

fruitfulness of the results and/or methods employed as these are connected to the problem under

investigation. If the particular results suggest no further studies, then they would seem to be a

sort of dead end. But if particular methods and results suggest a further hypothesis, then we have

5

a better idea of how to continue a particular line of inquiry. Seeking an objective basis for

preference among untested hypotheses, one may hope to avoid not merely subjectivism but also

over-emphasis on consensus and externally motivated consensus seeking. Likewise, if we have a

way of ordering hypotheses independent of new empirical tests, then we are in a better position

to resist the influence of money, media, and political or institutional rigidities as these may affect

the weighting of alternative hypotheses and proposals for research.

The notion of abduction goes missing in Karl Popper’s writings, and this in spite of his

generally positive relationship to Peirce. Popper usually speaks of “conjecture” where others

might be inclined to speak of abduction, or “inference to the best explanation.” Plausibly, an

initial comparative evaluation of hypotheses cannot be completely separated from the ways in

which they are tested or might be tested, so that Peircean abduction, deduction and induction

tend to combine in many contexts; and that is to be expected, even welcomed. That a given

scientific proposal is testable, or at least prospectively testable, certainly lends it higher standing.

We find a similar combination in Popper, given the prevalence of the phrase “conjecture and

refutation.” Beyond that, there are some suggestions of a quasi-logic of abduction (general

grounds for preference among as yet untested conjectures) in Popper’s writings. In Objective

Knowledge, Popper briefly characterizes his conception of conjecture in relation to “the method

of science”: “The method of science,” he says, “is the method of bold conjectures and ingenious

and severe attempts to refute them;” and “a bold conjecture is a theory with great content—

greater at any rate than the theory which, we are hoping, will be superseded by it.” Popper

continues:

That our conjectures should be bold follows immediately from what I have said about the aim of

science and the approach to truth: boldness, or great content, is linked with great truth content; for

this reason, the falsity content can at first be ignored.6

For Popper, a bold conjecture is to be preferred to a less bold conjecture, or at least he wants a

bolder conjecture, a theory of greater content, than what is contained in the theory we hope to

6. Karl Popper 1979, Objective Knowledge, revised edition (Oxford: O. U. P.), p. 81.

6

supplant. Popper’s position stands in considerable tension with a preference for more

conservative and modest hypotheses which tend more to projections of pre-existing theory and

results.7 “Our conjectures should be bold,” says Popper. “Great content” or greater content is to

be preferred. For Popper, if we want a comparative evaluation of two new theories, where the

two theories each contain an alternative new hypotheses, then we should prefer that alternative

theory and (and thus) hypothesis which makes for greater content. This is to say that in the

comparative evaluation of a pair of new hypotheses, suggested as needed modifications of some

pre-existing theory, we should generally prefer that new theory, containing an hypothesis, which

together have greater logical comprehension, implying a larger range of testable consequences.

But contrast physicist Brian Greene: “rather than trying through one leap, to incorporate all we

know about the physical universe in developing a new theory, it is often far more profitable to

take many small steps that sequentially include the newest discoveries from the forefront of

research.”8 This claim compares more favorably with Popper’s emphasis on “trial and error” and

the “piecemeal approach” in The Poverty of Historicism (1957), and equally with Popper’s

emphasis on simplicity in The Open Universe (1982).9

Einstein’s departures from Newtonian physics were bold indeed—and in the best sense. Yet

in spite of this apparent agreement between Popper’s account of preferable hypotheses and our

ex post facto preference for Einsteinian physics over Newtonian physics, there is some reason to

doubt that we can equate the “boldness” of Einstein’s departures from Newtonian physics with

Popper’s “boldness”—as a matter of “great” content or greater potential truth content—not, at

least, if we equate greater content with sheer numbers of claims implied by a theory or

something like the total number of its (additional) logical implications. Arguably, any formalized

theory will have an infinite or indefinite number of logical implications (consider only what we

7 . Notice that while Stephen Hawking expresses sympathy for Popper’s falsificationism, he says, too, that “In practice, it seems that one develops a new theory which in truth is only an extension of the old.” See, Hawking 2005, A Briefer History of Time, p. 20 in the German edition. (Hamburg: Rowohlt, 2006.)

8. Brian Greene 1999, The Elegant Universe (London: Vintage), p. 121. 9 . See Popper 1957 The Poverty of Historicism (London: Ark), p. 75; Popper 1982, The Open Universe

(London: Routledge), p. 44: “The method of science depends upon our attempts to describe the world in simple theories.”

7

can obtain by logic, adding one implication to another to form conjunctions), and in

consequence, we will not be able to reasonably explicate the boldness of alternative theories or

the comparative boldness of alternative theories purely in terms of the number of statements

implied. The intuitive sense of boldness which Popper employs, while it implies wider claims,

overall unity or greater prospective comprehension, does not seem to be equitable with any

simple conception of making wider claims, understood in terms of the number of logical

implications or the number of implications put directly at risk of falsification.

Intuitively, what is bold about Einstein in relation to Newtonian physics and other alternatives

to Newton proposed at the time, was his willingness to depart from accepted conceptions of

space and time. Before testing Einstein’s physics on its departures from the predictions of

Newtonian physics, we do not know that Einstein’s physics has greater content and greater truth

content than any possible alternative. Before testing, all we have to work with are the specific

implications of Einstein’s physics, the specific implications of Newtonian physics regarding the

same range of initial conditions, and the specific implications of alternatives to Einstein’s physics

(say, an alternative that attempted to treat the Einsteinian curvature of space-time as a matter of

light rays being subject to gravitational forces). Knowing of the success of Einsteinian physics in

relation to tests, we can indeed agree that it has “great content” and “great truth content,” but this

is not a kind of judgment we could reasonably make independent of our knowledge of its

experimental successes; and to that degree, Popper’s talk of boldness remains unexplicated.

What was bold about Einstein’s theory, was the bold departure from accepted conceptions

of space and time, but also his unifying treatment of space-time as part of the subject-matter

of physics, so that we could come to expect, as we now do, that massive objects interact with

the metric of space and time. Physical geometry, and the concept of time became innovatively

integrated with mechanics in ways which involve overall simplicity and comprehension of

approach. What is wanted, or sometimes wanted in any case, is precisely such startling new

8

comprehension and elegance: in Einstein’s case a uniform and integrated treatment of space,

time and matter in motion.

Boldness is indeed exactly what is wanted in a new hypothesis, sometimes; still my sense

of the matter is that Popper’s treatment of the theme is one-sided and too abstract. We do not

always reasonably prefer an hypothesis of great comprehension. Sometimes, what is preferred

is an hypothesis which makes minimal changes to accepted doctrine or theory and takes in an

apparent anomaly. This is the plausibility of the conservative or modest hypothesis. Such an

hypothesis will often be preferred to another which makes wider departures, even one which

portends greater comprehension. I think this is especially true, if relatively simple amendment

to, or augmentation of, an accepted theory promises ease of experimental testing. Though we

might expect the Peircean emphasis on continuity to bring him to favor conservative and

modest hypotheses, Peirce sometimes points in the opposite direction, warning “to be on your

guard against assuming anything to be true because it seems likely or a matter of course.”10

4. The Virtues of Hypotheses

One way to get an overview of the virtues of hypotheses is to see them as spanning the ever-

present gap between the universal aspiration and particular facts. We want a new hypothesis

and a theory with great comprehension so that, if it is correct, it will have a maximum

tendency to avoid future disappointments or disconfirmation. That is one of our methodologi-

cal ideals. Still, we have contrasting ideals. Though we want generality, we also want

testability, and connected with this is the ideal of preserving as much as possible of accepted

theory, even as we go about changing it in light of contrary evidence. No one would have

even considered Einstein’s physics, without the assurance that it came up with the same

predictions as Newtonian physics over the very wide range of circumstances in which Newto-

nian physics had succeeded in its predictions—so that even the boldest of hypotheses must

have its conservative side.

10. See Peirce 1898, in Ketner, K.L. and Hilary Putnam, ed. and Into., 1992, Reasoning and the Logic of Things, p.193.

9

Seeing the virtues of hypotheses as spanning the tensions between the particularity of

established fact and theory and ideal universality, as aiming us toward both predictive tests

and general explanatory intelligibility, the other virtues fall somewhere between, in somewhat

the following order: Refutability, conservatism, modesty, precision, elegance, generality. I

want to suggest a continuum of the virtues with contrasting extreme points, approximately,

from the virtues of the experimentalist to the virtues of the theoretician. (See fig. 1.)

If we follow Peirce in holding that “Logic may be defined as the science of the laws of the

stable establishment of beliefs,”11 then we may doubt that there is, or could be, a logic of

abduction which could establish stable beliefs regarding untested explanatory proposals on the

basis of laws. Our list of the virtues of explanatory hypotheses is not a matter of general laws,

since we have no general means of ranking the comparative importance of, say, conservatism

and modesty or simplicity, precision or generality for an arbitrarily selected context of

inquiry. In consequence, it seems we have no formal or law-like way to arrive at a generalized

ranking of competing hypotheses which exhibit these virtues. The named virtues are

comparative terms. One hypothesis is judged to be more easily refutable or more conserva-

tive, more modest, simpler, more precise or more general than another hypothesis in relation

to the same domain and context of inquiry, and the non-comparative, presumably monadic

predicates, “refutable,” conservative,” modest” “simple,” etc. borrow what sense they have

from the specific comparisons made in specific contexts. But even in a particular context of

inquiry, when we are dealing with a specific domain and accepted theory and its problems, if

we know exactly which of the proposed new explanatory hypotheses can be justly called more

easily refutable, more conservative, simpler, etc., this alone does not tell us which hypothesis

might best be accepted for preferential examination in that context of inquiry. It is not that

such judgments are not in fact made, and it is not that we cannot see the wisdom of examples.

11 . See Peirce, 1896 [CP 3.429], where he continues by defining “exact logic”: “Then, exact logic will be that doctrine of the conditions of establishment of stable belief which rests upon perfectly undoubted observations and upon mathematical, that is, upon diagrammatical, or, iconic, thought.”

10

But our assembly of convincing examples of preferences among the virtues, in the contexts of

particular inquiries, do not add up to a logic of abduction. On some occasions, generality

overrules simplicity or conservatism, on other occasions modesty or conservatism rightly

trumps generality or elegance. But if there were truly a logic of abduction, then we would

expect general rules or some stable ordering of the virtues across distinctive domains,

contexts and occasions of inquiry. Our esteem for any particular virtue in the order it provides

to a range of hypotheses on a particular occasion appears to be bound to the particular context

and otherwise chiefly retrospective and ex post facto: no generalized ordering of explanatory

hypotheses in terms of the virtues seems to be projectable across all domains and occasions of

inquiry: not conservatism, not boldness.

Notice that physics seems lately to have discounted modesty and even refutability as it has

explored the luxurious mathematical possibilities of string theory, drawn in this direction by

the prospect of a unified quantum-mechanical theory of the four known fundamental forces—

a prospective theory which would bridge and reconcile quantum mechanics and general

relativity. General relativity must break down, Stephen Hawking has argued, where the erst-

while continuities of curved space-time reach quantum-mechanical levels forbidding exact

continuity of competing measurements.12 As Brian Greene has put the point, “The notion of a

smooth spatial geometry, the central principle of general relativity, is destroyed by the violent

fluctuations of the quantum world on short distance scales.”13 Even at the time of Einstein’s

early work, though it was known that Newtonian physics didn’t correctly predict the orbits of

electrons around the atomic nucleus, the theory of relativity made only small and inadequate

correction to these false predictions. In this context we understand the significance of

Einstein’s role as the creator of relativity theory and as one of the chief thinkers responsible

12 . Cf. Stephen Hawking 2005, A Briefer History of Time: “…we know that the theory of general relativity must be modified. Because the classical (i.e. non quantum-mechanical) version predicts points of infinite density—singularities—it prognosticates its own failure…” See, p. 119 in the German edition.

13. Brian Greene 1999, p. 129.

11

for the birth of quantum mechanics.14 We see more clearly now, or believe more firmly, that

continuity of space, time and motion (though singularities are plausibly Peircean discontinui-

ties within Einstein’s physics) must give way to quantum-mechanical indeterminacies.

The beauty and generality of Einstein’s physics of space-time and gravitation seems to be

at war with the precision and predictive success of quantum mechanics; and Einstein’s later

dream of a unified field theory, though arguably more plausible during Einstein’s years at

Princeton, now counts as a proposal far wide of the mark, since the quantum-mechanical

approach has subsequently encompassed three of the four fundamental forces from the

opposite side.15 What counts as a more reasonable hypothesis or general direction of inquiry,

changes with, and thus depends upon, the specifics of our context of knowledge.

5. The Scientific Imagination

If there is strictly no logic of abduction, what does this tell us about pragmatism as a theory of

meaning? What we have learned is basically that there is no general smooth, continuous

projecting of accepted or established theory into the evaluation of modifying or supplemen-

tary hypotheses which arise in light of a problem in accepted and established theory. Peirce

himself says as much in some of his writings, warning against the domination of preconceived

ideas and plausibilities. Thus, in the first place, we must be concerned with the meaning of

existing or accepted theory and results and not that of the imagined ultimate theory at the

imagined end of inquiry. Yet this does not lead us to generally discounting conservatism and

modesty, or continuity, as virtues of proposed theory and hypothesis.

My conclusion is that in selecting among untested hypotheses, we have to do with a highly

contextual type of judgment, a kind of wisdom arising from the expert’s great familiarity with

14 . Einstein received the 1921 Nobel Prize in Physics, for his photoelectric law and work in the field of theoretical physics, thus chiefly for his work in the origin of quantum theory. Relativity, still under debate, was not mentioned.

15 . Still, as late as 1985, Richard Feynman wrote, with a somewhat skeptical tone that “Because the gravitational force is so much weaker than any of the other interactions, it is impossible at the present time to make any experiment that is sufficiently delicate to measure any effect that requires the precision of a quantum theory of gravitation to explain it.” See Feynman 1985, QED: The Strange Theory of Light and Matter (Princeton: PUP), p. 151.

12

the subject-matter. Deep familiarity with the details and problems of the domain of inquiry,

on the part of a master of the discipline, is the one commonality which bridges those cases

where we are inclined to favor bold generality and those where we are inclined to favor more

conservative, modest or easily testable alternatives. It is from this kind of perspective that we

judge of the lack of relevant experience, or the amateur status, of those offering only wild

guesses, as contrasted with educated guesswork. “Imagination uses an organic classification,”

we might say, while fancy “joins by accidental resemblances.” Basically, in knowing what to

count as potentially useful or more useful imaginative innovation and what to count as vain

fancy, we depend on detailed reference to the particular subject-matter in the continuity of

inquiry. In initial evaluation of hypotheses proposed, we must start from a detailed and

systematic account of past accomplishments in a field, together with the outstanding

anomalies and problems. It is out of this tension that the properly disciplined and genuinely

creative imagination arises.

(Draft of May 12, 2009)

Fig. 1

VIRTUES OF HYPOTHESES

(Particular) ←-------------------------------/ / /-----------------------------------------→ (Universal)

Excess: implausibility dogmatism meekness Übergenauigkeit16 naiveté rigidity

Virtue: Refutability Conservatism Modesty Precision Elegance Generality

Defect: self-insulation extravagance vanity vagueness complexity bias

(Experimentalist) ←---------------------------------/ / /------------------------------→ (Theoretician)

16. “Übergenauigkeit:” German: over-exactness, compare Latin: meticulosus: fearful.

13