As We May Think

By VANNEVAR BUSH

As Director of the Office of Scientific Research and Development, Dr. Vannevar Bush has coordinated
the activities of some six thousand leading American scientists in the application of science to
warfare. In this significant article he holds up an incentive for scientists when the fighting has
ceased. He urges that men of science should then turn to the massive task of making more accessible
our bewildering store of knowledge. For years inventions have extended man's physical powers rather
than the powers of his mind. Trip hammers that multiply the fists, microscopes that sharpen the
eye, and engines of destruction and detection are new results, but not the end results, of modern
science. Now, says Dr. Bush, instruments are at hand which, if properly developed, will give man
access to and command over the inherited knowledge of the ages. The perfection of these pacific
instruments should be the first objective of our scientists as they emerge from their war work.
Like Emerson's famous address of 1837 on "The American Scholar," this paper by Dr. Bush calls for a
new relationship between thinking man and the sum of our knowledge. —THE EDITOR

This has not been a scientist's war; it has been a war in which all have had a part. The
scientists, burying their old professional competition in the demand of a common cause, have shared
greatly and learned much. It has been exhilarating to work in effective partnership. Now, for many,
this appears to be approaching an end. What are the scientists to do next?

For the biologists, and particularly for the medical scientists, there can be little indecision,
for their war has hardly required them to leave the old paths. Many indeed have been able to carry
on their war research in their familiar peacetime laboratories. Their objectives remain much the
same.

It is the physicists who have been thrown most violently off stride, who have left academic
pursuits for the making of strange destructive gadgets, who have had to devise new methods for
their unanticipated assignments. They have done their part on the devices that made it possible to
turn back the enemy, have worked in combined effort with the physicists of our allies. They have
felt within themselves the stir of achievement. They have been part of a great team. Now, as peace
approaches, one asks where they will find objectives worthy of their best.

                                                 1

Of what lasting benefit has been man's use of science and of the new instruments which his research
brought into existence? First, they have increased his control of his material environment. They
have improved his food, his clothing, his shelter; they have increased his security and released
him partly from the bondage of bare existence. They have given him increased knowledge of his own
biological processes so that he has had a progressive freedom from disease and an increased span of
life. They are illuminating the interactions of his physiological and psychological functions,
giving the promise of an improved mental health.

Science has provided the swiftest communication between individuals; it has provided a record of
ideas and has enabled man to manipulate and to make extracts from that record so that knowledge
evolves and endures throughout the life of a race rather than that of an individual.

There is a growing mountain of research. But there is increased evidence that we are being bogged
down today as specialization extends. The investigator is staggered by the findings and conclusions
of thousands of other workers—conclusions which he cannot find time to grasp, much less to
remember, as they appear. Yet specialization becomes increasingly necessary for progress, and the
effort to bridge between disciplines is correspondingly superficial.

Professionally our methods of transmitting and reviewing the results of research are generations
old and by now are totally inadequate for their purpose. If the aggregate time spent in writing
scholarly works and in reading them could be evaluated, the ratio between these amounts of time
might well be startling. Those who conscientiously attempt to keep abreast of current thought, even
in restricted fields, by close and continuous reading might well shy away from an examination
calculated to show how much of the previous month's efforts could be produced on call. Mendel's
concept of the laws of genetics was lost to the world for a generation because his publication did
not reach the few who were capable of grasping and extending it; and this sort of catastrophe is
undoubtedly being repeated all about us, as truly significant attainments become lost in the mass
of the inconsequential.

The difficulty seems to be, not so much that we publish unduly in view of the extent and variety of
present day interests, but rather that publication has been extended far beyond our present ability
to make real use of the record. The summation of human experience is being expanded at a prodigious
rate, and the means we use for threading through the consequent maze to the momentarily important
item is the same as was used in the days of square-rigged ships.

But there are signs of a change as new and powerful instrumentalities come into use. Photocells
capable of seeing things in a physical sense, advanced photography which can record what is seen or
even what is not, thermionic tubes capable of controlling potent forces under the guidance of less
power than a mosquito uses to vibrate his wings, cathode ray tubes rendering visible an occurrence
so brief that by comparison a microsecond is a long time, relay combinations which will carry out
involved sequences of movements more reliably than any human operator and thousands of times as
fast—there are plenty of mechanical aids with which to effect a transformation in scientific
records.

Two centuries ago Leibnitz invented a calculating machine which embodied most of the essential
features of recent keyboard devices, but it could not then come into use. The economics of the
situation were against it: the labor involved in constructing it, before the days of mass
production, exceeded the labor to be saved by its use, since all it could accomplish could be
duplicated by sufficient use of pencil and paper. Moreover, it would have been subject to frequent
breakdown, so that it could not have been depended upon; for at that time and long after,
complexity and unreliability were synonymous.

Babbage, even with remarkably generous support for his time, could not produce his great
arithmetical machine. His idea was sound enough, but construction and maintenance costs were then
too heavy. Had a Pharaoh been given detailed and explicit designs of an automobile, and had he
understood them completely, it would have taxed the resources of his kingdom to have fashioned the
thousands of parts for a single car, and that car would have broken down on the first trip to Giza.

Machines with interchangeable parts can now be constructed with great economy of effort. In spite
of much complexity, they perform reliably. Witness the humble typewriter, or the movie camera, or
the automobile. Electrical contacts have ceased to stick when thoroughly understood. Note the
automatic telephone exchange, which has hundreds of thousands of such contacts, and yet is
reliable. A spider web of metal, sealed in a thin glass container, a wire heated to brilliant glow,
in short, the thermionic tube of radio sets, is made by the hundred million, tossed about in
packages, plugged into sockets—and it works! Its gossamer parts, the precise location and alignment
involved in its construction, would have occupied a master craftsman of the guild for months; now
it is built for thirty cents. The world has arrived at an age of cheap complex devices of great
reliability; and something is bound to come of it.

                                                 2

A record if it is to be useful to science, must be continuously extended, it must be stored, and
above all it must be consulted. Today we make the record conventionally by writing and photography,
followed by printing; but we also record on film, on wax disks, and on magnetic wires. Even if
utterly new recording procedures do not appear, these present ones are certainly in the process of
modification and extension.

Certainly progress in photography is not going to stop. Faster material and lenses, more automatic
cameras, finer-grained sensitive compounds to allow an extension of the minicamera idea, are all
imminent. Let us project this trend ahead to a logical, if not inevitable, outcome. The camera
hound of the future wears on his forehead a lump a little larger than a walnut. It takes pictures 3
millimeters square, later to be projected or enlarged, which after all involves only a factor of 10
beyond present practice. The lens is of universal focus, down to any distance accommodated by the
unaided eye, simply because it is of short focal length. There is a built-in photocell on the
walnut such as we now have on at least one camera, which automatically adjusts exposure for a wide
range of illumination. There is film in the walnut for a hundred exposures, and the spring for
operating its shutter and shifting its film is wound once for all when the film clip is inserted.
It produces its result in full color. It may well be stereoscopic, and record with two spaced glass
eyes, for striking improvements in stereoscopic technique are just around the corner.

The cord which trips its shutter may reach down a man's sleeve within easy reach of his fingers. A
quick squeeze, and the picture is taken. On a pair of ordinary glasses is a square of fine lines
near the top of one lens, where it is out of the way of ordinary vision. When an object appears in
that square, it is lined up for its picture. As the scientist of the future moves about the
laboratory or the field, every time he looks at something worthy of the record, he trips the
shutter and in it goes, without even an audible click. Is this all fantastic? The only fantastic
thing about it is the idea of making as many pictures as would result from its use.

Will there be dry photography? It is already here in two forms. When Brady made his Civil War
pictures, the plate had to be wet at the time of exposure. Now it has to be wet during development
instead. In the future perhaps it need not be wetted at all. There have long been films impregnated
with diazo dyes which form a picture without development, so that it is already there as soon as
the camera has been operated. An exposure to ammonia gas destroys the unexposed dye, and the
picture can then be taken out into the light and examined. The process is now slow, but someone may
speed it up, and it has no grain difficulties such as now keep photographic researchers busy. Often
it would be advantageous to be able to snap the camera and to look at the picture immediately.

Another process now in use is also slow, and more or less clumsy. For fifty years impregnated
papers have been used which turn dark at every point where an electrical contact touches them, by
reason of the chemical change thus produced in an iodine compound included in the paper. They have
been used to make records, for a pointer moving across them can leave a trail behind. If the
electrical potential on the pointer is varied as it moves, the line becomes light or dark in
accordance with the potential.

This scheme is now used in facsimile transmission. The pointer draws a set of closely spaced lines
across the paper one after another. As it moves, its potential is varied in accordance with a
varying current received over wires from a distant station, where these variations are produced by
a photocell which is similarly scanning a picture. At every instant the darkness of the line being
drawn is made equal to the darkness of the point on the picture being observed by the photocell.
Thus, when the whole picture has been covered, a replica appears at the receiving end.

A scene itself can be just as well looked over line by line by the photocell in this way as can a
photograph of the scene. This whole apparatus constitutes a camera, with the added feature, which
can be dispensed with if desired, of making its picture at a distance. It is slow, and the picture
is poor in detail. Still, it does give another process of dry photography, in which the picture is
finished as soon as it is taken.

It would be a brave man who would predict that such a process will always remain clumsy, slow, and
faulty in detail. Television equipment today transmits sixteen reasonably good pictures a second,
and it involves only two essential differences from the process described above. For one, the
record is made by a moving beam of electrons rather than a moving pointer, for the reason that an
electron beam can sweep across the picture very rapidly indeed. The other difference involves
merely the use of a screen which glows momentarily when the electrons hit, rather than a chemically
treated paper or film which is permanently altered. This speed is necessary in television, for
motion pictures rather than stills are the object.

Use chemically treated film in place of the glowing screen, allow the apparatus to transmit one
picture only rather than a succession, and a rapid camera for dry photography results. The treated
film needs to be far faster in action than present examples, but it probably could be. More serious
is the objection that this scheme would involve putting the film inside a vacuum chamber, for
electron beams behave normally only in such a rarefied environment. This difficulty could be
avoided by allowing the electron beam to play on one side of a partition, and by pressing the film
against the other side, if this partition were such as to allow the electrons to go through
perpendicular to its surface, and to prevent them from spreading out sideways. Such partitions, in
crude form, could certainly be constructed, and they will hardly hold up the general development.

Like dry photography, microphotography still has a long way to go. The basic scheme of reducing the
size of the record, and examining it by projection rather than directly, has possibilities too
great to be ignored. The combination of optical projection and photographic reduction is already
producing some results in microfilm for scholarly purposes, and the potentialities are highly
suggestive. Today, with microfilm, reductions by a linear factor of 20 can be employed and still
produce full clarity when the material is re-enlarged for examination. The limits are set by the
graininess of the film, the excellence of the optical system, and the efficiency of the light
sources employed. All of these are rapidly improving.

Assume a linear ratio of 100 for future use. Consider film of the same thickness as paper, although
thinner film will certainly be usable. Even under these conditions there would be a total factor of
10,000 between the bulk of the ordinary record on books, and its microfilm replica.
TheEncyclopoedia Britannica could be reduced to the volume of a matchbox. A library of a million
volumes could be compressed into one end of a desk. If the human race has produced since the
invention of movable type a total record, in the form of magazines, newspapers, books, tracts,
advertising blurbs, correspondence, having a volume corresponding to a billion books, the whole
affair, assembled and compressed, could be lugged off in a moving van. Mere compression, of course,
is not enough; one needs not only to make and store a record but also be able to consult it, and
this aspect of the matter comes later. Even the modern great library is not generally consulted; it
is nibbled at by a few.

Compression is important, however, when it comes to costs. The material for the
microfilmBritannica would cost a nickel, and it could be mailed anywhere for a cent. What would it
cost to print a million copies? To print a sheet of newspaper, in a large edition, costs a small
fraction of a cent. The entire material of the Britannica in reduced microfilm form would go on a
sheet eight and one-half by eleven inches. Once it is available, with the photographic reproduction
methods of the future, duplicates in large quantities could probably be turned out for a cent
apiece beyond the cost of materials. The preparation of the original copy? That introduces the next
aspect of the subject.

                                                 3

To make the record, we now push a pencil or tap a typewriter. Then comes the process of digestion
and correction, followed by an intricate process of typesetting, printing, and distribution. To
consider the first stage of the procedure, will the author of the future cease writing by hand or
typewriter and talk directly to the record? He does so indirectly, by talking to a stenographer or
a wax cylinder; but the elements are all present if he wishes to have his talk directly produce a
typed record. All he needs to do is to take advantage of existing mechanisms and to alter his
language.

At a recent World Fair a machine called a Voder was shown. A girl stroked its keys and it emitted
recognizable speech. No human vocal chords entered into the procedure at any point; the keys simply
combined some electrically produced vibrations and passed these on to a loud-speaker. In the Bell
Laboratories there is the converse of this machine, called a Vocoder. The loudspeaker is replaced
by a microphone, which picks up sound. Speak to it, and the corresponding keys move. This may be
one element of the postulated system.

The other element is found in the stenotype, that somewhat disconcerting device encountered usually
at public meetings. A girl strokes its keys languidly and looks about the room and sometimes at the
speaker with a disquieting gaze. From it emerges a typed strip which records in a phonetically
simplified language a record of what the speaker is supposed to have said. Later this strip is
retyped into ordinary language, for in its nascent form it is intelligible only to the initiated.
Combine these two elements, let the Vocoder run the stenotype, and the result is a machine which
types when talked to.

Our present languages are not especially adapted to this sort of mechanization, it is true. It is
strange that the inventors of universal languages have not seized upon the idea of producing one
which better fitted the technique for transmitting and recording speech. Mechanization may yet
force the issue, especially in the scientific field; whereupon scientific jargon would become still
less intelligible to the layman.

One can now picture a future investigator in his laboratory. His hands are free, and he is not
anchored. As he moves about and observes, he photographs and comments. Time is automatically
recorded to tie the two records together. If he goes into the field, he may be connected by radio
to his recorder. As he ponders over his notes in the evening, he again talks his comments into the
record. His typed record, as well as his photographs, may both be in miniature, so that he projects
them for examination.

Much needs to occur, however, between the collection of data and observations, the extraction of
parallel material from the existing record, and the final insertion of new material into the
general body of the common record. For mature thought there is no mechanical substitute. But
creative thought and essentially repetitive thought are very different things. For the latter there
are, and may be, powerful mechanical aids.

Adding a column of figures is a repetitive thought process, and it was long ago properly relegated
to the machine. True, the machine is sometimes controlled by a keyboard, and thought of a sort
enters in reading the figures and poking the corresponding keys, but even this is avoidable.
Machines have been made which will read typed figures by photocells and then depress the
corresponding keys; these are combinations of photocells for scanning the type, electric circuits
for sorting the consequent variations, and relay circuits for interpreting the result into the
action of solenoids to pull the keys down.

All this complication is needed because of the clumsy way in which we have learned to write
figures. If we recorded them positionally, simply by the configuration of a set of dots on a card,
the automatic reading mechanism would become comparatively simple. In fact if the dots are holes,
we have the punched-card machine long ago produced by Hollorith for the purposes of the census, and
now used throughout business. Some types of complex businesses could hardly operate without these
machines.

Adding is only one operation. To perform arithmetical computation involves also subtraction,
multiplication, and division, and in addition some method for temporary storage of results, removal
from storage for further manipulation, and recording of final results by printing. Machines for
these purposes are now of two types: keyboard machines for accounting and the like, manually
controlled for the insertion of data, and usually automatically controlled as far as the sequence
of operations is concerned; and punched-card machines in which separate operations are usually
delegated to a series of machines, and the cards then transferred bodily from one to another. Both
forms are very useful; but as far as complex computations are concerned, both are still in embryo.

Rapid electrical counting appeared soon after the physicists found it desirable to count cosmic
rays. For their own purposes the physicists promptly constructed thermionic-tube equipment capable
of counting electrical impulses at the rate of 100,000 a second. The advanced arithmetical machines
of the future will be electrical in nature, and they will perform at 100 times present speeds, or
more.

Moreover, they will be far more versatile than present commercial machines, so that they may
readily be adapted for a wide variety of operations. They will be controlled by a control card or
film, they will select their own data and manipulate it in accordance with the instructions thus
inserted, they will perform complex arithmetical computations at exceedingly high speeds, and they
will record results in such form as to be readily available for distribution or for later further
manipulation. Such machines will have enormous appetites. One of them will take instructions and
data from a whole roomful of girls armed with simple key board punches, and will deliver sheets of
computed results every few minutes. There will always be plenty of things to compute in the
detailed affairs of millions of people doing complicated things.

                                                 4

The repetitive processes of thought are not confined however, to matters of arithmetic and
statistics. In fact, every time one combines and records facts in accordance with established
logical processes, the creative aspect of thinking is concerned only with the selection of the data
and the process to be employed and the manipulation thereafter is repetitive in nature and hence a
fit matter to be relegated to the machine. Not so much has been done along these lines,beyond the
bounds of arithmetic, as might be done, primarily because of the economics of the situation. The
needs of business and the extensive market obviously waiting, assured the advent of mass-produced
arithmetical machines just as soon as production methods were sufficiently advanced.

With machines for advanced analysis no such situation existed; for there was and is no extensive
market; the users of advanced methods of manipulating data are a very small part of the population.
There are, however, machines for solving differential equations—and functional and integral
equations, for that matter. There are many special machines, such as the harmonic synthesizer which
predicts the tides. There will be many more, appearing certainly first in the hands of the
scientist and in small numbers.

If scientific reasoning were limited to the logical processes of arithmetic, we should not get far
in our understanding of the physical world. One might as well attempt to grasp the game of poker
entirely by the use of the mathematics of probability. The abacus, with its beads strung on
parallel wires, led the Arabs to positional numeration and the concept of zero many centuries
before the rest of the world; and it was a useful tool—so useful that it still exists.

It is a far cry from the abacus to the modern keyboard accounting machine. It will be an equal step
to the arithmetical machine of the future. But even this new machine will not take the scientist
where he needs to go. Relief must be secured from laborious detailed manipulation of higher
mathematics as well, if the users of it are to free their brains for something more than repetitive
detailed transformations in accordance with established rules. A mathematician is not a man who can
readily manipulate figures; often he cannot. He is not even a man who can readily perform the
transformations of equations by the use of calculus. He is primarily an individual who is skilled
in the use of symbolic logic on a high plane, and especially he is a man of intuitive judgment in
the choice of the manipulative processes he employs.

All else he should be able to turn over to his mechanism, just as confidently as he turns over the
propelling of his car to the intricate mechanism under the hood. Only then will mathematics be
practically effective in bringing the growing knowledge of atomistics to the useful solution of the
advanced problems of chemistry, metallurgy, and biology. For this reason there still come more
machines to handle advanced mathematics for the scientist. Some of them will be sufficiently
bizarre to suit the most fastidious connoisseur of the present artifacts of civilization.

                                                 5

The scientist, however, is not the only person who manipulates data and examines the world about
him by the use of logical processes, although he sometimes preserves this appearance by adopting
into the fold anyone who becomes logical, much in the manner in which a British labor leader is
elevated to knighthood. Whenever logical processes of thought are employed—that is, whenever
thought for a time runs along an accepted groove—there is an opportunity for the machine. Formal
logic used to be a keen instrument in the hands of the teacher in his trying of students' souls. It
is readily possible to construct a machine which will manipulate premises in accordance with formal
logic, simply by the clever use of relay circuits. Put a set of premises into such a device and
turn the crank, and it will readily pass out conclusion after conclusion, all in accordance with
logical law, and with no more slips than would be expected of a keyboard adding machine.

Logic can become enormously difficult, and it would undoubtedly be well to produce more assurance
in its use. The machines for higher analysis have usually been equation solvers. Ideas are
beginning to appear for equation transformers, which will rearrange the relationship expressed by
an equation in accordance with strict and rather advanced logic. Progress is inhibited by the
exceedingly crude way in which mathematicians express their relationships. They employ a symbolism
which grew like Topsy and has little consistency; a strange fact in that most logical field.

A new symbolism, probably positional, must apparently precede the reduction of mathematical
transformations to machine processes. Then, on beyond the strict logic of the mathematician, lies
the application of logic in everyday affairs. We may some day click off arguments on a machine with
the same assurance that we now enter sales on a cash register. But the machine of logic will not
look like a cash register, even of the streamlined model.

So much for the manipulation of ideas and their insertion into the record. Thus far we seem to be
worse off than before—for we can enormously extend the record; yet even in its present bulk we can
hardly consult it. This is a much larger matter than merely the extraction of data for the purposes
of scientific research; it involves the entire process by which man profits by his inheritance of
acquired knowledge. The prime action of use is selection, and here we are halting indeed. There may
be millions of fine thoughts, and the account of the experience on which they are based, all
encased within stone walls of acceptable architectural form; but if the scholar can get at only one
a week by diligent search, his syntheses are not likely to keep up with the current scene.

Selection, in this broad sense, is a stone adze in the hands of a cabinetmaker. Yet, in a narrow
sense and in other areas, something has already been done mechanically on selection. The personnel
officer of a factory drops a stack of a few thousand employee cards into a selecting machine, sets
a code in accordance with an established convention, and produces in a short time a list of all
employees who live in Trenton and know Spanish. Even such devices are much too slow when it comes,
for example, to matching a set of fingerprints with one of five million on file. Selection devices
of this sort will soon be speeded up from their present rate of reviewing data at a few hundred a
minute. By the use of photocells and microfilm they will survey items at the rate of a thousand a
second, and will print out duplicates of those selected.

This process, however, is simple selection: it proceeds by examining in turn every one of a large
set of items, and by picking out those which have certain specified characteristics. There is
another form of selection best illustrated by the automatic telephone exchange. You dial a number
and the machine selects and connects just one of a million possible stations. It does not run over
them all. It pays attention only to a class given by a first digit, then only to a subclass of this
given by the second digit, and so on; and thus proceeds rapidly and almost unerringly to the
selected station. It requires a few seconds to make the selection, although the process could be
speeded up if increased speed were economically warranted. If necessary, it could be made extremely
fast by substituting thermionic-tube switching for mechanical switching, so that the full selection
could be made in one one-hundredth of a second. No one would wish to spend the money necessary to
make this change in the telephone system, but the general idea is applicable elsewhere.

Take the prosaic problem of the great department store. Every time a charge sale is made, there are
a number of things to be done. The inventory needs to be revised, the salesman needs to be given
credit for the sale, the general accounts need an entry, and, most important, the customer needs to
be charged. A central records device has been developed in which much of this work is done
conveniently. The salesman places on a stand the customer's identification card, his own card, and
the card taken from the article sold—all punched cards. When he pulls a lever, contacts are made
through the holes, machinery at a central point makes the necessary computations and entries, and
the proper receipt is printed for the salesman to pass to the customer.

But there may be ten thousand charge customers doing business with the store, and before the full
operation can be completed someone has to select the right card and insert it at the central
office. Now rapid selection can slide just the proper card into position in an instant or two, and
return it afterward. Another difficulty occurs, however. Someone must read a total on the card, so
that the machine can add its computed item to it. Conceivably the cards might be of the dry
photography type I have described. Existing totals could then be read by photocell, and the new
total entered by an electron beam.

The cards may be in miniature, so that they occupy little space. They must move quickly. They need
not be transferred far, but merely into position so that the photocell and recorder can operate on
them. Positional dots can enter the data. At the end of the month a machine can readily be made to
read these and to print an ordinary bill. With tube selection, in which no mechanical parts are
involved in the switches, little time need be occupied in bringing the correct card into use—a
second should suffice for the entire operation. The whole record on the card may be made by
magnetic dots on a steel sheet if desired, instead of dots to be observed optically, following the
scheme by which Poulsen long ago put speech on a magnetic wire. This method has the advantage of
simplicity and ease of erasure. By using photography, however one can arrange to project the record
in enlarged form and at a distance by using the process common in television equipment.

One can consider rapid selection of this form, and distant projection for other purposes. To be
able to key one sheet of a million before an operator in a second or two, with the possibility of
then adding notes thereto, is suggestive in many ways. It might even be of use in libraries, but
that is another story. At any rate, there are now some interesting combinations possible. One
might, for example, speak to a microphone, in the manner described in connection with the speech
controlled typewriter, and thus make his selections. It would certainly beat the usual file clerk.

                                                 6

The real heart of the matter of selection, however, goes deeper than a lag in the adoption of
mechanisms by libraries, or a lack of development of devices for their use. Our ineptitude in
getting at the record is largely caused by the artificiality of systems of indexing. When data of
any sort are placed in storage, they are filed alphabetically or numerically, and information is
found (when it is) by tracing it down from subclass to subclass. It can be in only one place,
unless duplicates are used; one has to have rules as to which path will locate it, and the rules
are cumbersome. Having found one item, moreover, one has to emerge from the system and re-enter on
a new path.

The human mind does not work that way. It operates by association. With one item in its grasp, it
snaps instantly to the next that is suggested by the association of thoughts, in accordance with
some intricate web of trails carried by the cells of the brain. It has other characteristics, of
course; trails that are not frequently followed are prone to fade, items are not fully permanent,
memory is transitory. Yet the speed of action, the intricacy of trails, the detail of mental
pictures, is awe-inspiring beyond all else in nature.

Man cannot hope fully to duplicate this mental process artificially, but he certainly ought to be
able to learn from it. In minor ways he may even improve, for his records have relative permanency.
The first idea, however, to be drawn from the analogy concerns selection. Selection by association,
rather than indexing, may yet be mechanized. One cannot hope thus to equal the speed and
flexibility with which the mind follows an associative trail, but it should be possible to beat the
mind decisively in regard to the permanence and clarity of the items resurrected from storage.

Consider a future device for individual use, which is a sort of mechanized private file and
library. It needs a name, and, to coin one at random, "memex" will do. A memex is a device in which
an individual stores all his books, records, and communications, and which is mechanized so that it
may be consulted with exceeding speed and flexibility. It is an enlarged intimate supplement to his
memory.

It consists of a desk, and while it can presumably be operated from a distance, it is primarily the
piece of furniture at which he works. On the top are slanting translucent screens, on which
material can be projected for convenient reading. There is a keyboard, and sets of buttons and
levers. Otherwise it looks like an ordinary desk.

In one end is the stored material. The matter of bulk is well taken care of by improved microfilm.
Only a small part of the interior of the memex is devoted to storage, the rest to mechanism. Yet if
the user inserted 5000 pages of material a day it would take him hundreds of years to fill the
repository, so he can be profligate and enter material freely.

Most of the memex contents are purchased on microfilm ready for insertion. Books of all sorts,
pictures, current periodicals, newspapers, are thus obtained and dropped into place. Business
correspondence takes the same path. And there is provision for direct entry. On the top of the
memex is a transparent platen. On this are placed longhand notes, photographs, memoranda, all sorts
of things. When one is in place, the depression of a lever causes it to be photographed onto the
next blank space in a section of the memex film, dry photography being employed.

There is, of course, provision for consultation of the record by the usual scheme of indexing. If
the user wishes to consult a certain book, he taps its code on the keyboard, and the title page of
the book promptly appears before him, projected onto one of his viewing positions. Frequently-used
codes are mnemonic, so that he seldom consults his code book; but when he does, a single tap of a
key projects it for his use. Moreover, he has supplemental levers. On deflecting one of these
levers to the right he runs through the book before him, each page in turn being projected at a
speed which just allows a recognizing glance at each. If he deflects it further to the right, he
steps through the book 10 pages at a time; still further at 100 pages at a time. Deflection to the
left gives him the same control backwards.

A special button transfers him immediately to the first page of the index. Any given book of his
library can thus be called up and consulted with far greater facility than if it were taken from a
shelf. As he has several projection positions, he can leave one item in position while he calls up
another. He can add marginal notes and comments, taking advantage of one possible type of dry
photography, and it could even be arranged so that he can do this by a stylus scheme, such as is
now employed in the telautograph seen in railroad waiting rooms, just as though he had the physical
page before him.

                                                 7

All this is conventional, except for the projection forward of present-day mechanisms and gadgetry.
It affords an immediate step, however, to associative indexing, the basic idea of which is a
provision whereby any item may be caused at will to select immediately and automatically another.
This is the essential feature of the memex. The process of tying two items together is the
important thing.

When the user is building a trail, he names it, inserts the name in his code book, and taps it out
on his keyboard. Before him are the two items to be joined, projected onto adjacent viewing
positions. At the bottom of each there are a number of blank code spaces, and a pointer is set to
indicate one of these on each item. The user taps a single key, and the items are permanently
joined. In each code space appears the code word. Out of view, but also in the code space, is
inserted a set of dots for photocell viewing; and on each item these dots by their positions
designate the index number of the other item.

Thereafter, at any time, when one of these items is in view, the other can be instantly recalled
merely by tapping a button below the corresponding code space. Moreover, when numerous items have
been thus joined together to form a trail, they can be reviewed in turn, rapidly or slowly, by
deflecting a lever like that used for turning the pages of a book. It is exactly as though the
physical items had been gathered together from widely separated sources and bound together to form
a new book. It is more than this, for any item can be joined into numerous trails.

The owner of the memex, let us say, is interested in the origin and properties of the bow and
arrow. Specifically he is studying why the short Turkish bow was apparently superior to the English
long bow in the skirmishes of the Crusades. He has dozens of possibly pertinent books and articles
in his memex. First he runs through an encyclopedia, finds an interesting but sketchy article,
leaves it projected. Next, in a history, he finds another pertinent item, and ties the two
together. Thus he goes, building a trail of many items. Occasionally he inserts a comment of his
own, either linking it into the main trail or joining it by a side trail to a particular item. When
it becomes evident that the elastic properties of available materials had a great deal to do with
the bow, he branches off on a side trail which takes him through textbooks on elasticity and tables
of physical constants. He inserts a page of longhand analysis of his own. Thus he builds a trail of
his interest through the maze of materials available to him.

And his trails do not fade. Several years later, his talk with a friend turns to the queer ways in
which a people resist innovations, even of vital interest. He has an example, in the fact that the
outraged Europeans still failed to adopt the Turkish bow. In fact he has a trail on it. A touch
brings up the code book. Tapping a few keys projects the head of the trail. A lever runs through it
at will, stopping at interesting items, going off on side excursions. It is an interesting trail,
pertinent to the discussion. So he sets a reproducer in action, photographs the whole trail out,
and passes it to his friend for insertion in his own memex, there to be linked into the more
general trail.

                                                 8

Wholly new forms of encyclopedias will appear, ready made with a mesh of associative trails running
through them, ready to be dropped into the memex and there amplified. The lawyer has at his touch
the associated opinions and decisions of his whole experience, and of the experience of friends and
authorities. The patent attorney has on call the millions of issued patents, with familiar trails
to every point of his client's interest. The physician, puzzled by a patient's reactions, strikes
the trail established in studying an earlier similar case, and runs rapidly through analogous case
histories, with side references to the classics for the pertinent anatomy and histology. The
chemist, struggling with the synthesis of an organic compound, has all the chemical literature
before him in his laboratory, with trails following the analogies of compounds, and side trails to
their physical and chemical behavior.

The historian, with a vast chronological account of a people, parallels it with a skip trail which
stops only on the salient items, and can follow at any time contemporary trails which lead him all
over civilization at a particular epoch. There is a new profession of trail blazers, those who find
delight in the task of establishing useful trails through the enormous mass of the common record.
The inheritance from the master becomes, not only his additions to the world's record, but for his
disciples the entire scaffolding by which they were erected.

Thus science may implement the ways in which man produces, stores, and consults the record of the
race. It might be striking to outline the instrumentalities of the future more spectacularly,
rather than to stick closely to methods and elements now known and undergoing rapid development, as
has been done here. Technical difficulties of all sorts have been ignored, certainly, but also
ignored are means as yet unknown which may come any day to accelerate technical progress as
violently as did the advent of the thermionic tube. In order that the picture may not be too
commonplace, by reason of sticking to present-day patterns, it may be well to mention one such
possibility, not to prophesy but merely to suggest, for prophecy based on extension of the known
has substance, while prophecy founded on the unknown is only a doubly involved guess.

All our steps in creating or absorbing material of the record proceed through one of the senses—the
tactile when we touch keys, the oral when we speak or listen, the visual when we read. Is it not
possible that some day the path may be established more directly?

We know that when the eye sees, all the consequent information is transmitted to the brain by means
of electrical vibrations in the channel of the optic nerve. This is an exact analogy with the
electrical vibrations which occur in the cable of a television set: they convey the picture from
the photocells which see it to the radio transmitter from which it is broadcast. We know further
that if we can approach that cable with the proper instruments, we do not need to touch it; we can
pick up those vibrations by electrical induction and thus discover and reproduce the scene which is
being transmitted, just as a telephone wire may be tapped for its message.

The impulses which flow in the arm nerves of a typist convey to her fingers the translated
information which reaches her eye or ear, in order that the fingers may be caused to strike the
proper keys. Might not these currents be intercepted, either in the original form in which
information is conveyed to the brain, or in the marvelously metamorphosed form in which they then
proceed to the hand?

By bone conduction we already introduce sounds: into the nerve channels of the deaf in order that
they may hear. Is it not possible that we may learn to introduce them without the present
cumbersomeness of first transforming electrical vibrations to mechanical ones, which the human
mechanism promptly transforms back to the electrical form? With a couple of electrodes on the skull
the encephalograph now produces pen-and-ink traces which bear some relation to the electrical
phenomena going on in the brain itself. True, the record is unintelligible, except as it points out
certain gross misfunctioning of the cerebral mechanism; but who would now place bounds on where
such a thing may lead?

In the outside world, all forms of intelligence whether of sound or sight, have been reduced to the
form of varying currents in an electric circuit in order that they may be transmitted. Inside the
human frame exactly the same sort of process occurs. Must we always transform to mechanical
movements in order to proceed from one electrical phenomenon to another? It is a suggestive
thought, but it hardly warrants prediction without losing touch with reality and immediateness.

Presumably man's spirit should be elevated if he can better review his shady past and analyze more
completely and objectively his present problems. He has built a civilization so complex that he
needs to mechanize his records more fully if he is to push his experiment to its logical conclusion
and not merely become bogged down part way there by overtaxing his limited memory. His excursions
may be more enjoyable if he can reacquire the privilege of forgetting the manifold things he does
not need to have immediately at hand, with some assurance that he can find them again if they prove
important.

The applications of science have built man a well-supplied house, and are teaching him to live
healthily therein. They have enabled him to throw masses of people against one another with cruel
weapons. They may yet allow him truly to encompass the great record and to grow in the wisdom of
race experience. He may perish in conflict before he learns to wield that record for his true good.
Yet, in the application of science to the needs and desires of man, it would seem to be a
singularly unfortunate stage at which to terminate the process, or to lose hope as to the outcome.