The Scientific Imagination

It is quite generally recognized that imagination is indispensable in

all sciences; that without it we could only copy, repeat, imitate; that

it is a stimulus driving us onward and launching us into the unknown. If

there does exist a very widespread prejudice to the contrary--if many

hold that scientific culture throttles imagination--we must look for the

explanation of this view first, in the equivocation, pointed out several

times, that makes the essence of the creative imagination consist of

images, which are here most often replaced by abstractions or extracts

of things--whence it results that the created work does not have the

living forms of religion, of art, or even of mechanical invention; and

then, in the rational requirements regulating the development of the

creative faculty--it may not wander at will. In either case its end is

determined, and in order to exist, i.e., in order to be accepted, the

invention must become subject to preestablished rules.

This variety of imagination being, after the esthetic form, the one

that psychologists have best described, we may therefore be brief. A

complete study of the subject, however, remains yet to be made. Indeed,

we may remark that there is no "scientific imagination" in general, that

its form must vary according to the nature of the science, and that,

consequently, it really resolves itself into a certain number of genera

and even of species. Whence arises the need of monographs, each one of

which should be the work of a competent man.

No one will question that mathematicians have a way of thinking all

their own; but even this is too general. The arithmetician, the

algebraist, and more generally the analyst, in whom invention obtains in

the most abstract form of discontinuous functions--symbols and their

relations--cannot imagine like the geometrician. One may well speak of

the ideal figures of geometry--the empirical origin of which is no

longer anywhere contested--but we cannot escape from representing them

as somehow in space. Does anyone think that Monge, the creator of

descriptive geometry, who by his work has aided builders, architects,

mechanics, stone cutters in their labors, could have the same type of

imagination as the mathematician who has been given up all his life to

the theory of number? Here, then, are at least two well-marked

varieties, to say nothing of mixed forms. The physicist's imagination is

necessarily more concrete; since he is incessantly obliged to refer to

the data of sense or to that totality of visual, tactile, motor,

acoustic, thermic, etc., representations that we term the "properties

of matter." Our eye, says Tyndall, cannot see sound waves contract and

dilate, but we construct them in thought--i.e., by means of visual

images. The same remarks are true of chemists. The founders of the

atomic theory certainly saw atoms, and pictured them in the mind's

eye, and their arrangement in compound bodies. The complexity of the

imagination increases still more in the geologist, the botanist, the

zoologist; it approaches more and more, with its increasing details, to

the level of perception. The physician, in whom science becomes also an

art, has need of visual representations of the exterior and interior,

microscopic and macroscopic, of the various forms of diseased

conditions; auditory representations (auscultation); tactile

representations (touch, reverberation, etc.); and let us also add that

we are not speaking merely of diagnosis of diseases, which is a matter

of reproductive imagination, but of the discovery of a new pathologic

"entity," proven and made certain from the symptoms. Lastly, if we do

not hesitate to give a very broad extension to the term "scientific,"

and apply it also to invention in social matters, we shall see that the

latter is still more exacting, for one must represent to oneself not

only the elements of the past and of the present, but in addition

construct a picture of the future according to probable inductions and


It might be objected that the foregoing enumeration proves a great

variety in the content of creative imagination but not in the

imagination itself, and that nothing has proven that, under all these

various aspects, there does not exist a so-called scientific

imagination, that always remains identical. This position is untenable.

For we have seen above that there exists no creative instinct in

general, no one mere indeterminate "creative power," but only wants

that, in certain cases, excite novel combinations of images. The nature

of the separable materials, then, is a factor of the first importance;

it is determining, and indicates to the mind the direction in which it

is turned, and all treason in this regard is paid for by aborted

construction, by painful labor for some petty result. Invention,

separated from what gives it body and soul, is nothing but a pure


The monographs called for above would, then, be a not unneeded work. It

is only from them collectively that the role of the imagination in the

sciences could be completely shown, and we might by abstraction separate

out the characters common to all varieties--the essential marks of this

imaginative type.

Mathematics aside, all the sciences dealing with facts--from astronomy

to sociology--suppose three moments, namely, observation, conjecture,

verification. The first depends on external and internal sense, the

second on the creative imagination, the third on rational operations,

although the imagination is not entirely barred from it. In order to

study its influence on scientific development, we shall study it (a) in

the sciences in process of formation; (b) in the established sciences;

(c) in the processes of verification.


It has often been said that the perfection of a science is measured by

the amount of mathematics it requires; we might say, conversely, that

its lack of completeness is measured by the amount of imagination that

it includes. It is a psychological necessity. Where the human mind

cannot explain or prove, there it invents; preferring a semblance of

knowledge to its total absence. Imagination fulfills the function

of a substitute; it furnishes a subjective, conjectural solution in

place of an objective, rational explanation. This substitution has


(1) The sway of the imagination is almost complete in the

pseudo-sciences (alchemy, astrology, magic, occultism, etc.), which it

would be more proper to call embryonic sciences, for they were the

beginnings of more exact disciplines and their fancies have not been

without use. In the history of science, this is the golden age of the

creative imagination, corresponding to the myth-making period already


(2) The semi-sciences, incompletely proved (certain portions of

biology, psychology, sociology, etc.), although they show a regression

of imaginative explanation repulsed by the hitherto absent or

insufficient experimentation, nevertheless abound in hypotheses, that

succeed, contradict, destroy one another. It is a commonplace truism

that does not need to be dwelt on--they furnish ad libitum examples of

what has been rightly termed scientific mythology.

Aside from the quantity of imagination expended, often without great

profit, there is another character to be noted--the nature of the belief

that accompanies imaginative creation. We have already seen repeatedly

that the intensity of the imaginary conception is in direct ratio to the

accompanying belief, or rather, that the two phenomena are really

one--merely the two aspects of one and the same state of consciousness.

But faith--i.e., the adherence of the mind to an undemonstrated

assertion--is here at its maximum.

There are in the sciences hypotheses that are not believed in, that are

preserved for their didactic usefulness, because they furnish a simple

and convenient method of explanation. Thus the "properties of matter"

(heat, electricity, magnetism, etc.), regarded by physicists as distinct

qualities even in the first half of the last century; the "two electric

fluids;" cohesion, affinity, etc., in chemistry--these are some of the

convenient and admitted expressions to which, however, we attach no

explanatory value.

There is also to be mentioned the hypothesis held as an approximation

of reality--this is the truly scientific position. It is accompanied by

a provisional and ever-revocable belief. This is admitted, in principle

at least, by all scientists, and has been put into practice by many of


Lastly, there is the hypothesis regarded as the truth itself--one that

is accompanied by a complete, absolute, belief. But daily observation

and history show us that in the realm of embryonic and ill-proven

sciences this disposition is more flourishing than anywhere else. The

less proof there is, the more we believe. This attitude, however wrong

from the standpoint of the logician, seems to the psychologist natural.

The mind clings tenaciously to the hypothesis because the latter is its

own creation, or, because in adopting it, it seems to the mind that it

should have itself discovered the hypothesis, so much does the latter

harmonize with its inner states. Let us take the hypothesis of

evolution, for example: we need not mention its high philosophical

bearing, and the immense influence that it exerts on almost all forms of

human thought. Nevertheless, it still remains an hypothesis; but for

many it is an indisputable and inviolable dogma, raised far above all

controversy. They accept it with the uncompromising fervor of believers:

a new proof of the underlying connection between imagination and

belief--they increase and decrease pari passu.


Should we assign as belonging solely to the imagination every invention

or discovery--in a word, whatever is new--in the well-organized sciences

that form a body of solid, constantly-broadening doctrine? It is a hard

question. That which raises scientific knowledge above popular knowledge

is the use of an experimental method and rigorous reasoning processes;

but, is not induction and deduction going from the known to the unknown?

Without desiring to depreciate the method and its value, it must

nevertheless be admitted that it is preventive, not inventive. It

resembles, says Condillac, the parapets of a bridge, which do not help

the traveler to walk, but keep him from falling over. It is of value

especially as a habit of mind. People have wisely discoursed on the

"methods" of invention. There are none; but for which fact we could

manufacture inventors just as we make mechanics and watchmakers. It is

the imagination that invents, that provides the rational faculties with

their materials, with the position, and even the solution of their

problems. Reasoning is only a means for control and proof; it transforms

the work of the imagination into acceptable, logical results. If one has

not imagined beforehand, the logical method is aimless and useless, for

we cannot reason concerning the completely unknown. Even when a problem

seems to advance towards solution wholly through the reason, the

imagination ceaselessly intervenes in the form of a succession of

groupings, trials, guesses, and possibilities that it proposes. The

function of method is to determine its value, to accept or reject


Let us show by a few examples that conjecture, the work of the combining

imagination, is at the root of the most diverse scientific


Every mathematical invention is at first only an hypothesis that must be

demonstrated, i.e., must be brought under previously established

general principles: prior to the decisive moment of rational

verification it is only a thing imagined. "In a conversation concerning

the place of imagination in scientific work," says Liebig, "a great

French mathematician expressed the opinion to me that the greater part

of mathematical truth is acquired not through deduction, but through the

imagination. He might have said 'all the mathematical truths,' without

being wrong." We know that Pascal discovered the thirty-second

proposition of Euclid all by himself. It is true that it has been

concluded, wrongly perhaps, that he had also discovered all the earlier

ones, the order followed by the Greek geometrician not being necessary,

and not excluding other arrangements. However it be, reasoning alone was

not enough for that discovery. "Many people," says Naville, "of whom I

am one, might have thought hard all their lives without finding out the

thirty-two propositions of Euclid." This fact alone shows clearly the

difference between invention and demonstration, imagination and reason.

In the sciences dealing with facts, all the best-established

experimental truths have passed through a conjectural stage. History

permits no doubt on this point. What makes it appear otherwise is the

fact that for centuries there has gradually come to be formed a body of

solid belief, making a whole, stored away in classic treatises from

which we learn from childhood, and in which they seem to be arranged of

themselves. We are not told of the series of checks and failures through

which they have passed. Innumerable are the inventions that

remained for a long time in a state of conjecture, matters of pure

imagination, because various circumstances did not permit them to take

shape, to be demonstrated and verified. Thus, in the thirteenth century,

Roger Bacon had a very clear idea of a construction on rails similar to

our railroads; of optical instruments that would permit, as does the

telescope, to see very far, and to discover the invisible. It is even

claimed that he must have foreseen the phenomena of interferences, the

demonstration of which had to be awaited ten centuries.

On the other hand, there are guesses that have met success without much

delay, but in which the imaginative phase--that of the invention

preceding all demonstration--is easy to locate. We know that

Tycho-Brahe, lacking inventive genius but rich in capacity for exact

observation, met Kepler, an adventurous spirit: together, the two made a

complete scientist. We have seen how Kepler, guided by a preconceived

notion of the "harmony of the spheres," after many trials and

corrections, ended by discovering his laws. Copernicus recognized

expressly that his theory was suggested to him by an hypothesis of

Pythagoras--that of a revolution of the earth about a central fire,

assumed to be in a fixed position. Newton imagined his hypothesis of

gravitation from the year 1666 on, then abandoned it, the result of his

calculations disagreeing with observation; finally he took it up again

after a lapse of a few years, having obtained from Paris the new measure

of the terrestrial meridian that permitted him to prove his guess. In

relating his discoveries, Lavoisier is lavish in expressions that leave

no doubt as to their originally conjectural character. "He suspects

that the air of the atmosphere is not a simple thing, but is composed of

two very different substances." "He presumes that the permanent

alkalies (potash, soda) and the earths (lime, magnesia) should not be

considered simple substances." And he adds: "What I present here is at

the most no more than a mere conjecture." We have mentioned above the

case of Darwin. Besides, the history of scientific discoveries is full

of facts of this sort.

The passage from the imaginative to the rational phase may be slow or

sudden. "For eight months," says Kepler, "I have seen a first glimmer;

for three months, daylight; for the last week I see the sunlight of the

most wonderful contemplation." On the other hand, Hauey drops a bit of

crystallized calcium spar, and, looking at one of the broken prisms,

cries out, "All is found!" and immediately verifies his quick intuition

in regard to the true nature of crystallization. We have already

indicated the psychological reasons for these differences.

Underneath all the reasoning, inductions, deductions, calculations,

demonstrations, methods, and logical apparatus of every sort, there is

something animating them that is not understood, that is the work of

that complex operation--the constructive imagination.

To conclude: The hypothesis is a creation of the mind, invested with a

provisional reality that may, after verification, become permanent.

False hypotheses are characterized as imaginary, by which designation is

meant that they have not become freed from the first state. But for

psychology they are different neither in their origin nor in their

nature from those scientific hypotheses that, subjected to the power of

reason or of experiment, have come out victorious. Besides, in addition

to abortive hypotheses, there are dethroned ones. What theory was more

clinging, more fascinating in its applications, than that of phlogiston?

Kant praised it as one of the greatest discoveries of the

eighteenth century. The development of the sciences is replete with

these downfalls. They are psychological regressions: the invention,

considered for a time as adequate to reality, decays, returns to the

imaginative phase whence it seems to have emerged, and remains pure



Imagination is not absent from the third stage of scientific research,

in demonstration and experimentation, but here we must be brief, (1)

because it passes to a minor place, yielding its rank to other modes of

investigation, and (2) because this study would have to become doubly

employed with the practical and mechanical imagination, which will

occupy our attention later. The imagination is here only an auxiliary, a

useful instrument, serving:

(1) In the sciences of reasoning, to discover ingenious methods of

demonstration, stratagems for avoiding or overcoming difficulties.

(2) In the experimental sciences for inventing methods of research or of

control--whence its analogy, above mentioned, to the practical

imagination. Furthermore, the reciprocal influence of these two forms of

imagination is a matter of common observation: a scientific discovery

permits the invention of new instruments; the invention of new

instruments makes possible experiments that are increasingly more

complicated and delicate.

One remark further: This constructive imagination at the third stage is

the only one met with in many scientists. They lack genius for

invention, but discover details, additions, corrections, improvements. A

recent author distinguishes (a) those who have created the hypothesis,

prepared the experiments, and imagined the appropriate apparatus; (b)

those who have imagined the hypothesis and the experiment, but use means

already invented; and (c) those who, having found the hypothesis made

and demonstrated, have thought out a new method of verification.

The scientific imagination becomes poorer as we follow it down this

scale, which, however, bears no relation to exactness of reasoning and

firmness of method.

Neglecting species and varieties, we may reduce the fundamental

characters of the scientific imagination to the following:

For its material, it has concepts, the degree of abstraction of which

varies with the nature of the science.

It employs only those associational forms that have an objective basis,

although its mission is to form new combinations, "the discoveries

consisting of the relation of ideas, capable of being united, which

hitherto have been isolated." (Laplace.) All association with an

affective basis is strictly excluded.

It aims toward objectivity: in its conjectural construction it attempts

to reproduce the order and connection of things. Whence its natural

affinity for realistic art, which is midway between fiction and reality.

It is unifying, and so just the opposite of the esthetic imagination,

which is rather developmental. It puts forward the master idea (Claude

Bernard's idee directrice), a center of attraction and impulse that

enlivens the entire work. The principle of unity, without which no

creation succeeds, is nowhere more visible than in the scientific

imagination. Even when illusory, it is useful. Pasteur, scrupulous

scientist that he was, did not hesitate to say: "The experimenter's

illusions are a part of his power: they are the preconceived ideas

serving as guides for him."


It does not seem to me wrong to regard the imagination of the

metaphysician as a variety of the scientific imagination. Both arise

from one and the same requirement. Several times before this we have

emphasized this point--that the various forms of imagination are not the

work of an alleged "creative instinct," but that each particular one has

arisen from a special need. The scientific imagination has for its prime

motive the need of partial knowledge or explanation; the metaphysical

imagination has for its prime motive the need of a total or complete

explanation. The latter is no longer an endeavor on a restricted group

of phenomena, but a conjecture as to the totality of things, as

aspiration toward completely unified knowledge, a need of final

explanation that, for certain minds, is just as imperious as any other


This necessity is expressed by the creation of a cosmic or human

hypothesis constructed after the type and methods of scientific

hypotheses, but radically subjective in its origin--only apparently

objective. It is a rationalized myth.

The three moments requisite for the constitution of a science are found

here, but in a modified form: reflection replaces observation, the

choice of the hypothesis becomes all-important, and its application to

everything corresponds to scientific proof.

(1) The first moment or preparatory stage, does not belong to our

subject. It requires, however, a word in passing. In all science,

whether well or ill established, firm or weak, we start from facts

derived from observation or experiment. Here, facts are replaced by

general ideas. The terminus of every science is, then, the

starting-point of philosophical speculation:--metaphysics begins where

each separate science ends; and the limits of the latter are theories,

hypotheses. These hypotheses become working material for metaphysics

which, consequently, is an hypothesis built on hypotheses, a conjecture

grafted on conjecture, a work of imagination superimposed on works of

imagination. Its principal source, then, is imagination, to which

reflection applies itself.

Metaphysicians, indeed, hold that the object of their researches, far

from being symbolic and abstract, as in science, or fictitious and

imaginary, as in art, is the very essence of things,--absolute reality.

Unfortunately, they have never proven that it suffices to seek in order

to find, and to wish in order to get.

(2) The second stage is critical. It is concerned with finding the

principle that rules and explains everything. In the invention of his

theory the metaphysician gives his measure, and permits us to value his

imaginative power. But the hypothesis, which in science is always

provisional and revocable, is here the supreme reality, the fixed

position, the inconcussum quid.

The choice of the principle depends on several causes: The chief of

these is the creator's individuality. Every metaphysician has a point of

view, a personal way of contemplating and interpreting the totality of

things, a belief that tends to recruit adherents.

Secondary causes are: the influence of earlier systems, the sum of

acquired knowledge, the social milieu, the variable predominance of

religions, sciences, morality, esthetic culture.

Without troubling ourselves with classifications, otherwise very

numerous, into which we may group systems (idealism, materialism,

monism, etc.) we shall, for our purpose, divide metaphysicians into the

imaginative and rational, according as the imagination is superior to

the reason or the reason rules the imagination. The differences between

these two types of mind, already clearly shown in the choice of the

hypothesis, are proven in its development.

(3) The fundamental principle, indeed, must come out of its state of

involution and justify its universal validity by explaining everything.

This is the third moment, when the scientific process of verification is

replaced by a process of construction.

All imaginative metaphysics have a dynamic basis, e.g., the Platonic

Ideas, Leibniz' Monadology, the Nature-philosophy of Schelling,

Schopenhauer's Will, and Hartmann's Unconscious, the mystics, the

systems that assume a world-soul, etc. Semi-abstract, semi-poetic

constructions, they are permeated with imagination not only in the

general conception, but also in the numberless details of its

application. Such are the "fulgurations" of Leibniz, those very rich

digressions of Schopenhauer, etc. They have the fascination of a work of

art as much as that of science, and this is no longer questioned by

metaphysicians themselves; they are living things.

Rational metaphysics, on the other hand, have a chilly aspect, which

brings them nearer the abstract sciences. Such are most of the

mechanical conceptions, the Hegelian Dialectic, Spinoza's construction

more geometrico, the Summa of the Middle Ages. These are buildings

of concepts solidly cemented together with logical relations. But art is

not wholly absent; it is seen in the systematic concatenation, in the

beautiful ordering, in the symmetry of division, in the skill with which

the generative principle is constantly brought in, in showing it

ever-present, explaining everything. It has been possible to compare

these systems with the architecture of the Gothic cathedrals, in which

the dominant idea is incessantly repeated in the numberless details of

the construction, and in the branching multiplicity of ornamentation.

Further, whatever view we adopt as to its ultimate value, it must be

recognized that the imagination of the great metaphysicians, by the

originality and fearlessness of its conceptions, by its skill in

perfecting all parts of its work, is inferior to no other form. It is

equal to the highest, if it does not indeed surpass them.