Induction and Retroduction

A couple years ago, I posted an essay here called “What is Eduction,” spelling out part of a framework I’ve found helpful for analyzing processes of media transduction.  I’d now like to follow up with a similar essay centered on two more pieces of the same framework: induction and retroduction.  Much as with eduction, these categories encompass processes generally felt to define particular modern technologies of communication and representation, such as “taking” photographs or “playing back” recorded motions, but they’re simultaneously broader in scope and have greater historical depth.  However revolutionary the introduction of photography or phonography (in the Edisonian sense) may have been in certain respects, mainly their novel strategies for harnessing the action of light and sound, they partook in other respects of some long-term continuities.  And just to be clear, I’m addressing the processes themselves here, and not the cultural constraints on their application, as with—say—the extension of preexisting conventions of portraiture to portrait photography.  Written accounts contemporaneous with the introduction of these processes tended to emphasize whatever was new and revolutionary about them, since that’s what commentators found exciting or demanding of explanation at the time.  The continuities can be more challenging to pinpoint because they often involve elements that contemporaries instead took for granted.  Eductionism is intended in large measure to expose these continuities by (1) tracing historical developments in eduction, induction, and retroduction; and (2) applying techniques of eduction creatively to historical materials—sometimes in ways that qualify as retroduction, and sometimes not.

Like my earlier essay on eduction, this essay will be somewhat meandering and tentative—it’s more a record of my ongoing brainstorming efforts than a polished statement of theory.  But I’m not sure when (or if) I’ll have the leisure to write up these thoughts more formally, and since much of the work I present here at Griffonage-Dot-Com has been drawing on them for inspiration and guidance, I hate to leave them hidden and unexpressed.  After all, my work here isn’t all just about the novelty of making pictures talk, sing, move, and morph (for example); there’s a why to it all which hinges on teasing out important themes in the history of media, inscription, communication, and art—on making them vivid, tangible, transparent, and conspicuous where they might otherwise be abstract, opaque, and easy to ignore.

For present purposes, I’ll say that transduction refers to changes in the material modality of “content”—data, energy, a signal, etc.—that don’t rely on anyone cognitively or subjectively processing it.  Some work might be needed to set the process up, make it happen, or keep it going, and a lot of thought and artistry might go into initiating it and setting its parameters, but the actual transition between modalities runs its course automatically and indexically as patterns in the first modality result in patterns in the second modality.  Some common kinds of modality for transduction are patterns of light, sound vibrations, fluctuations of electric current, and static material shapes.  Thus, a microphone transduces sound vibrations into fluctuations of electric current, and a traditional photographic camera transduces dynamic patterns of light into static material structures.

There are two subcategories of transduction which I like to distinguish.  Induction is input transduction, where content passes into a system (without anyone needing to attend to details in order for them to make it in); while eduction is output transduction, where content passes out of a system (either enabling people to perceive it and process it or feeding into another system in turn).

Sometimes induction and eduction are clearly separate processes, as with a telephone system: induction is what a transmitter does in converting sound vibrations into an electrical signal, and eduction is what a receiver does in converting an electrical signal into sound vibrations.  In other cases, the processes may be more intimately intertwined, as in shadow puppetry: the use of a distinctively shaped puppet to block light is arguably induction (transducing forms into the “system”), and the receipt of a three-dimensional pattern of light and darkness on a flat screen from which it’s passed on to the viewer in turn is arguably eduction (transducing forms out of the “system” for perception), but the one leads so directly to the other that it may intuitively seem more appropriate to think about them in terms of a single act that simultaneously has aspects of “in” and “out” to it.  Even in such cases, though, I’d suggest that the distinction is a heuristically useful one.  I think we run less risk of making simple cases seem too complicated than we do of making complicated cases seem too simple.

We might sometimes also identify a whole chain of transductions (with each step divisible into further sub-steps), as for instance: patterns of light → photographic negative → photographic print → half-tone photographic negative → half-tone printing plate → half-tone print → digital scan → uncompressed digital file → compressed digital file → display on computer screen → patterns of light.  Each intermediate step has its inbox and its outbox.

If content is induced and then educed in turn to generate sensory stimuli that meaningfully resemble those associated with the “original,” I call this retroduction.  I don’t say “reproduction,” because there shouldn’t be any assumption here of exact duplication.  There’s a resemblance, and it’s based on cause and effect—that’s all.  Shadows are a good example of retroduction: they resemble the things that cast them, but only in certain respects, so that they aren’t likely to be thought of as “duplicates” of those things.  In photography, too, patterns of light can be induced as structures in the stuff of a photosensitive surface; material patterns can be educed as patterns of light by reflecting light off a photographic print; and if the educed patterns resemble the induced ones, then the eduction also counts as retroduction.  It’s with the playback of recorded sounds that people most often confuse retroductions with “reproductions,” but the technical principle in that case is the same as with shadows and photographs, even if there’s a lot of cultural baggage that suggests otherwise.

We could educe a freehand pencil sketch of a person’s face in the same way we educe the photographic print, by reflecting light off its surface, but this wouldn’t be a case of retroduction because the content of the sketch wouldn’t have come about through induction.  The sketch can certainly resemble its subject, but if so, it’s due to human observation and human mimetic skill, and not because of any direct chain of cause and effect.  Here I want to distinguish acts of transduction from what I’ll call acts of fashioning: those inscriptive processes where each and every meaningful detail involves human intervention and free will, as with traditional forms of writing, painting, drawing, and sculpting.  Oliver Wendell Holmes famously expressed the difference in connection with photography as follows:

Theoretically, a perfect photograph is absolutely inexhaustible. In a picture you can find nothing the artist has not seen before you; but in a perfect photograph there will be as many beauties lurking, unobserved, as there are flowers that blush unseen in forests and meadows…. The very things which an artist would leave out, or render imperfectly, the photograph takes infinite care with, and so makes its illusions perfect. (“The Stereoscope and the Stereograph,” Atlantic Monthly 3 [June 1859], 738-748, at 744, 746, online here.)

Thus, a painter would need to decide consciously to include a loose strand of hair in a portrait, and what it ought to look like, whereas a photographer wouldn’t: the detail could make it into the picture unnoticed.  And there’s also the “perfection” of the overall “illusion,” such as the capture of a person’s recognizable likeness.  If a freehand painted portrait looks like its subject, the explanation for why it does so is obviously very different from the explanation for why a photograph might look like its subject.  The first resemblance comes about  through conscious fashioning that reflects an artist’s observations and impressions, while the second resemblance comes about through a chain of cause and effect in which none of the links depends on the intervention of a human brain.

I’m not aware of any established terms for what I’m calling fashioning on the one hand and induction on the other, and I’ve often been frustrated in the past trying to express the distinction between them clearly and succinctly.  Naming these categories is an important step towards making it possible to talk about them.  That said, I’ve proposed a contrast between two other terms elsewhere that embodies much the same distinction: induction relies by definition on an autographic (“self-writing”) logic of representation, in which forms are caused to re-present themselves indexically in some new modality, while fashioning relies by definition on allographic (“other-writing”) strategies of representation, in which forms are manipulated into shape by entities other than themselves.  (I’m aware that the terms autographic and allographic have also been put to other uses, most famously by Nelson Goodman; but others, notably James Lastra, have used autographic in the same sense I’m adopting here, and allographic is an obvious choice for its antonym.)


There are complications, of course, which is where it gets interesting.  It’s not at all rare for individual cases to involve both fashioning and induction simultaneously.  A prime example is the use of molds, printing plates, and the like.  Thus, the creation of an ancient cylinder seal involved meticulous fashioning, but impressions made from it in turn are strictly induced.

cylinder-sealMoreover, the seal has been carefully fashioned as a negative so that its details are vertically and laterally reversed; it was intended not for direct viewing, but only to serve as a means for inducing positive copies, which had a profound impact in turn on the form it took and the skills required to make it.  Any writing, for example, would have had to be formed as a mirror image (except for boustrophedon writing, which would have been uniquely well suited to this scenario).  Many other comparable cases could be adduced from history: the casting of spearheads and daggers, the coining of coins, the molding of lamps and figurines, the stamping of bricks and tiles, woodblock printing on textiles and paper, and so forth.  Each of these cases involved the fashioning of an original for the express purpose of inducing multiple tokens of its fashioned form.  Originals in this spirit include molds, matrices, dies, stamps, stencils, and printing plates, to list a few terms and varieties.  Their creation can be a multi-step, multi-generation process, as with lost-wax casting where a negative mold is formed around a positive wax original and the wax is then melted out to leave a cavity.

We can refer to any subject designated for induction as an inducendum (Latin: “thing to be induced”), plural inducenda; and any object that results from induction as an inductum (Latin: “thing that has been induced”), plural inducta.  Some straightforward examples of inducenda : inducta are die : coin, mold : cast, and printing plate : print.

But inducenda needn’t always have been fashioned with induction in mind.  They can also be chosen and repurposed from pre-existing reality.  Take, for instance, a terracotta “squeeze” prepared by Nabonidus of the Neo-Babylonian Empire (556-539 BC) from an original stone inscription of Shar-kali-sharri of the Akkadian Empire (ca. 2200 BC), which you can read about here:

This is a 2500-year-old facsimile made from a historical inscription that was itself 1650 years old at the time, with descriptive metadata added in cuneiform on the reverse, and it was made through a process of induction parallel to the process of digitizing a historical document on a flatbed scanner today.  (I had the privilege of holding it in my hand during a wonderful visit to the tablet room at Penn Museum with curator Steve Tinney in April 2015.)

The process of making rubbings of monumental brasses, gravestones, and so forth, clearly falls into a shared category with Nabonidus’s “squeeze,” as it does with paper squeezes made by pressing moistened paper against monumental inscriptions and other such surfaces.  I can’t begin to do justice to the history of such techniques here, but the earliest use of rubbing which the Oxford English Dictionary lists as a noun in this sense dates from 1833:

CASTS or rubbings from Inscriptions, are of the greatest utility, and much preferable to drawings; because, unless the Draftsman perfectly understands the characters as well as the language of the original—unless the mind instructs the eye and guides the pencil,—he will never be enabled to make a correct copy of the object before him.  If there should be an accidental blemish on the stone, he will perhaps insert it as part of a letter, or if a connecting line or member be indistinct, then perhaps he will wholly omit it, supposing the faint trace to be a blemish. (C. P. Cooper, February 1833.)

This approach to facsimile-making was apparently known in 1799-1800 when the French took relief and intaglio prints of the freshly-discovered Rosetta Stone in Egypt for study back in Europe.  But in China, similar facsimile-making on paper can be traced back considerably further than that, as Wu Hung observes (in A Story of Ruins, pp. 51-2):

The technique of rubbing gained currency in the West no earlier than the nineteenth century, when antiquarians began to use a crayon-like agent to record inscriptions and designs on tombstones.  But in China, ink rubbings made from engraved words and images had appeared by at least the sixth century.  During the following centuries, this technique gradually developed into a major means of preserving ancient engravings and transmitting famous calligraphy.

The same author goes on to discuss the history of rubbings of one particular stele as it deteriorated over the course of centuries (A Story of Ruins, pp. 57-8).  It would be interesting to gather all these rubbings, place them in chronological order, and create a time-lapse animation of the deterioration of the stele—maybe one of my readers in China can give this idea a try.  Meanwhile, a comparable practice in Japan is oshigata (押形), in which a rubbing is made of the signature on the nakago or tang of a traditionally crafted sword.  The list of examples could go on and on.  What ties all these practices together is that they extend the principle of induction to human artifacts that weren’t fashioned with duplication in mind.  We might draw a distinction here between premeditated inducenda, or things conceived of as inducenda at the time of their making, and fortuitous inducenda, or things that have been repurposed as inducenda but originally came into being under circumstances unrelated to induction.

Historically, it appears that some well-known categories of premeditated inducenda may have originated as categories of fortuitous inducenda.  According to Wikipedia, for example: “Engraving on metal was part of the goldsmith’s craft throughout the Medieval period, and the idea of printing engraved designs onto paper probably began as a method for them to record the designs on pieces they had sold.”  The origin of cuneiform writing, as wonderfully reconstructed by Denise Schmandt-Besserat, is likewise interesting to recast in these terms.  At first, Mesopotamian accountants tracked commodities by means of three-dimensional clay tokens: an ovoid represented a jar of oil, a cone represented a small measure of grain, a sphere represented a large measure of grain, and so forth.  Sometimes a group of these tokens was sealed inside a clay envelope, perhaps documenting a debt; and at some point the practice arose of pressing the tokens into the outside of the envelope before it was sealed to leave a record of them which could be consulted without prematurely breaking open the envelope.  Eventually, people stopped inserting the tokens and simply made do with the impressions they made into slabs of clay that evolved into the cuneiform tablet.  What interests Schmandt-Besserat is that the impressions made by cones and spheres took on abstract numerical meanings and were augmented—and finally superseded—by patterns composed piecemeal with a stylus.  But at some point in this process, the cones and spheres would also appear to have ceased to be fortuitous inducenda, three-dimensional tokens to be manipulated directly in accounting, and to have instead become premeditated inducenda whose primary purpose was to leave distinctive impressions (inducta) of themselves, much like seal-rings: not counters any longer, but stamps.  This process reminds me of the one by which two formerly independent species begin to interact with each other more and more closely and then evolve in ways that make them mutually dependent for their survival on their symbiotic relationship.

To take things one step further, inducenda might not even be human artifacts in the first place.  Indeed, a process of induction can play itself out with no human intervention whatsoever—consider the various processes of fossilization.  But often the induction is human-initiated, and only the subject is “natural.”  This is true of masks molded from people’s faces, for example, whether life masks or death masks.  In either case, we might speak of natural inducenda as contrasted with fashioned inducenda.  (Since the former are a subcategory of fortuitous inducenda, it might sometimes be helpful to distinguish fortuitous fashioned inducenda in turn, such as the Rosetta Stone.)  And we could call fossils natural inducta, while artifacts created inductively through purposeful human intervention, such as life masks, could be called artificial inducta.

The different categories of inducenda and inducta can be variously combined.  Fossils are natural inducta of natural inducenda, for instance, while coins are artificial inducta of premeditated inducenda.  However, one combination stands out as especially important in the evolution of modern technologies of representation: artificial inducta of natural inducenda.  These have a very long history.  Many prehistoric cave paintings take the form of hand stencils.  Some of these were dated not long ago to an age of at least 39,900 years; and even more recently the date of the earliest examples has been pushed back even further to 64,800 years ago (in Europe during Neanderthal times, before the arrival there of modern humans).  Hand stencils are geographically widespread, spanning Europe, East Asia, and South America, and are assumed to have been created by pressing a hand against the cave wall and blowing pigment—often red ocher—over it through a straw or pipe.  Here’s an example (photograph by Mariano Cecowski):

Hand prints are found as well, made by coating the hand itself with pigment and pressing it against the wall.  As of the latest reports I’ve seen, the oldest hand stencils are right up there in age with the earliest known fashioned figurative paintings, like those of bison, aurochs, and so forth, which some commentators speculate that they predated and inspired, as we see here:

“To me this is beginning to look like a plausible scenario for how humans invented figurative art,” [Paul Pettitt of Durham University] says. “It’s not so surprising that our ancestors would place this important natural tool on a wall and trace it. It will then occur to these people that they have created an outline… and that if a hand can be represented in outline, so can anything else.”

If Pettitt is right, the hand stencil was how our ancestors discovered that a three-dimensional object could be represented with a two-dimensional line.

As I discussed in connection with cave paintings in general in my essay on eduction, these hand stencils and hand prints were also formed in places with no natural source of light and would have needed to be lit by some kind of torch or lamp to become visible.  Complex processes of induction and eduction would both have been involved.  The hands are ordinarily human, but some 8,000-year-old stencils of the forefeet of monitor lizards have been identified, at least tentatively, among stencils of human hands on a rock wall in the Sahara Desert.

Another important category of artificial inducta of natural inducenda that partly overlaps the previous one is the “nature print,” which is covered admirably by Roderick Cave’s Impressions of Nature: A History of Nature Printing.  The nature print extends the principle of printing or rubbing on paper or similar materials to natural inducenda, the most typical subject being leaves.  Other terms for nature printing are typographia naturalis (Benjamin Martin, 1772) and Naturselbstdruck (Alois Auer, 1850s).  Despite the nominal emphasis on “nature” or “natural” subjects, practitioners sometimes applied the same techniques indiscriminately both to natural objects such as leaves, feathers, and so forth (i.e., natural inducenda), and to human artifacts such as lace (i.e., fortuitous fashioned inducenda).  The subject matter of “nature printing” as a whole is thus better characterized as fortuitous inducenda, whether natural or fashioned, rather than natural inducenda per se.  But this kind of slippage is common when it comes to such versatile processes.  We often characterize a technology of representation in terms of its most impressive capability, tacitly subsuming less impressive capabilities within it.  It’s easy to imagine someone speaking casually of photographing a marble statue or a dead body “from life.”  (Or, for that matter, seeing the Mona Lisa “in the flesh,” as a vernacular expression of co-presence.)

Sometimes nature printing has entailed inking an object such as a leaf in order to make a single, unique print from it.  In Japanese tradition, gyotaku (魚拓) is one such method of making prints from the bodies of fish, typically said to date back to the mid-nineteenth century.  However, much of the technological “progress” in nature printing has lain in developing methods by which many prints could be obtained from a single source object.  Thus, for example, Joseph Breintnall and Benjamin Franklin took casts of leaves to prepare copper printing plates that could withstand repeated use.  An early example appeared Poor Richard’s Almanack for 1737, published in 1736 in an edition of about ten thousand copies, apparently containing ten thousand prints of the same leaf.

Although it became possible to obtain many more-or-less identical prints from a single source leaf in this way, there was no means available at the time of making identical prints from a print in turn.  With that in mind, leaf prints were soon put to practical use as a design element in American paper currency, with “counterfeit detector” sheets printed on differently colored paper being circulated as a tool for authentication.  This scheme depended on the capacity of nature printing to represent natural forms with a degree of complexity, precision, and accuracy which the human eye could recognize through side-by-side comparison, but which the human hand could not replicate through conscious fashioning.  (The image below comes from the collections of the Library Company of Philadelphia.)

The term “nature print” is somewhat more slippery than I’ve acknowledged so far, though, since it was sometimes also used to refer to preserving actual natural specimens, as we see in its application to lepidochromy.  The Scientific American Supplement for May 11, 1889, glosses lepidochromy as the “decalcomania of butterflies”; it involved pressing the wings of insects between pieces of mucilage-coated paper to transfer the wing scales.  The most ambitious publication to use lepidochromy was Sherman F. Denton’s As Nature Shows Them: Moths and Butterflies of the United States East of the Rocky Mountains (1900, available online with volume one here; volume two here), the title page of which contrasts “photographic illustrations” (which it also contained) with the “transfers of species from life.”  As Denton wrote (1:vi):

The colored plates, or Nature Prints, used in the work, are direct transfers from the insects themselves; that is to say, the scales of the wings of the insects are transferred to the paper while the bodies are printed from engravings and afterward colored by hand.  The making of such transfers is not original with me, but it took a good deal of experimenting to so perfect the process as to make the transfers, on account of their fidelity to detail and their durability, fit for uses as illustrations in such a work.  And what magnificent illustrations they are, embodying all the beauty and perfection of the specimens themselves!

As I have had to make over fifty thousand of these transfers for the entire edition, not being able to get any one to help me who would do the work as I desired it done, and as more than half the specimens from which they were made were collected by myself, I having made many trips to different parts of the country for their capture, some idea of the labor in connection with preparing the material for the publication may be obtained.

Published in a limited edition of 500, each copy of As Nature Shows Them incorporated fifty pairs of front and back “transfers” of the wing scales of actual moths and butterflies.  Here are scans of the “upper side” transfers of Danais archippus from three different copies of the book (here, here, and here), each made from a different butterfly:

The analogy which the Scientific American drew between lepidochromy and decalcomania is informative.  Decalcomania, or the art of the “decal,” entails transferring a design from one surface (such as a flat sheet of paper) onto another surface (such as a rounded piece of pottery).  The act of transfer in this sense doesn’t properly constitute induction, I think, since a pattern isn’t induced from one material embodiment into another; the same material embodiment is merely relocated.  Lepidochromy involves a similarly limited act of transfer, as do such practices as pressing seaweed (flattening it through pressure against a sheet of paper in the interest of storage, display, or sale).  It strikes me as more akin to taxidermy, or to even less intrusive acts of collecting and recontextualizing, all centered on capturing things themselves, rather than representations of them formed out of alien material (a leaf print is not a leaf, and does not “contain” a leaf or any part or residue of one).

How does this distinction play out in the case of audio?  When sound vibrations are “converted” into an electrical signal or into undulations in the form of a groove on a wax cylinder, or vice versa, we can certainly speak of transduction.  By contrast, when sounds pass through a speaking tube, or enter a hearing trumpet, or exit a megaphone, I don’t believe we can: the sounds are relocated, or rechanneled, but they don’t undergo any material change in modality.  In such instances, we’re trading in the things themselves.  In this light, let’s review the claim advanced by Eric W. Rothenbuhler and John Durham Peters (“Defining Phonography: An Experiment in Theory,” Musical Quarterly 81 [1997]: 242-64, at 245-6, emphasis added):

The crucial difference between phonographic techniques and digital recording and playback is that the digital storage medium holds no analog of either the original recorded signal or the resulting playback.  The digital storage medium holds numbers—data….  Indeed, the idea that we buy music when we buy a CD is a holdover from phonography; actually, there is no music there.  By contrast, the phonograph record and the analog magnetic tape do contain physical traces of the music….  The hills and valleys of those grooves are physical analogs of the vibrations of the music….  When we buy a record we buy music, and when we buy a CD we buy data.

I find parts of this argument analogous to claiming that if we buy a print of a leaf in ink on paper, we buy a leaf, whereas if we download a digital photograph of a leaf, we get only data about a leaf.  In fact, both are representations of leaves, in contradistinction to (say) a real leaf pressed between the pages of a book.  If the ink print “contains a physical trace of the leaf,” or the gramophone disc “contains physical traces of the music,” it’s in the sense that a footprint is a physical trace left by a foot, and not in the sense that fish contain trace amounts of mercury.  The footprint physically shares the contour of a foot, which we could arguably recreate in the round by making a plaster cast; but there’s no foot there.  What we mean when we speak of “analog” media is that the content of the carrier physically shares a contour or shape in common with whatever it represents; in other words, it assumes an analogous physical form.  But, of course, an analogy isn’t an analogy if source and target are not merely similar, but identical (“sound is to ear as sound is to…..?”).

I’m less certain how the framework I’ve proposed should apply to the mechanical (“tin can” or “string”) telephone, in which sound vibrations pass from one membrane to another along a string but retain their character as vibrations throughout.  I feel intuitively that the membrane still transduces the sound vibrations; after all, they’re “picked up” from the air in fundamentally the same way as they are in a phonograph or an electric telephone.  And yet there’s arguably no change in modality in this case, no point at which sound waves cease to propagate according to ordinary physical principles and become something else.  Sound passes into the string via the membrane just as it would pass into, say, a window or a wall.  Presuming that the propagated vibration is the thing itself, we would seem to be dealing here with something analogous to lepidochromy rather than something analogous to a leaf print.  One way out of this dilemma would be to posit that a change in the medium of a compression wave qualifies as a sufficient material change in modality to constitute transduction.  An aerial sound wave passing into a wall or window would then be a type of natural induction, like the creation of fossils.


There are also hybrid cases in which fashioning has been guided by eduction, or in which eduction has been modified by fashioning.  Consider the claim set forth in the opening lines of Book XXXV of the Natural History of Pliny the Elder, given below in Latin followed by my own English translation (since existing translations struck me as overly loose):

De picturae initiis incerta nec instituti operis quaestio est.  Aegyptii sex milibus annorum aput ipsos inventam, priusquam in Graeciam transiret, adfirmant, vana praedicatione, ut palam est; Graeci autem alii Sicyone, alii aput Corinthios repertam, omnes umbra hominis lineis circumducta….

Of the beginnings of painting, the question is uncertain and not of the work at hand.  The Egyptians assert it was invented among themselves six thousand years before it passed over into Greece, vain proclamation as it plainly is; the Greeks assert, however, some that it was invented at Sicyon, and some among the Corinthians, but all by means of the drawn-around shadow of a human being….

The parts of my translation shown in boldface are explicit in the original Latin, while the other parts are my own inferences.  The casting of shadows on a flat(tish) surface, while later exploited as the mechanism of shadow puppetry, can plainly also occur through natural induction and would surely have caught the attention of the first people to carry a lamp into the recesses of a formerly unlit cave.  But what do we make of the act of tracing around a shadow on a wall?  The creation of hand stencils, which we considered earlier, entails straightforward induction.  Drawing the shape of a hand freehand, based on observation or memory, would entail straightforward fashioning.  But I’d argue that tracing the outline of a shadow falls somewhere in the middle: an ephemeral form has already been set up through induction, and fashioning is used only to render that preexisting form more durable.  Or consider the analogous case of the pre-photographic camera obscura, which uses a lens or pinhole to induce a pattern of light “from nature” onto a flat surface from which it is visibly educed in turn, with the two processes together constituting retroduction; guided by that retroduction, an artist might then fashion static material patterns in paint or pencil or ink which can also be visibly educed as patterns of light.  We might similarly analyze the camera lucida as a drawing aid, the silhouette machine, the use of tracing paper for manual copying, or the processes outlined in Tim’s Vermeer.  Activities that otherwise seem to constitute fashioning, but that are narrowly guided in this way and so do not require or exploit much in the way of subjective discretion, might best be referred to as tracing (as opposed to the unguided sort of fashioning I had in mind when I chose the term “fashioning” in the first place).

Fashioning can also serve to augment induced inscriptions, as for example with the manual tinting or overpainting of photographic images.  And much as we have montages made up of “things themselves,” we also have composites fashioned manually out of induced elements which can often themselves be subject to induction in turn: consider the printing process in which various moveable type elements are assembled into a forme; a mold called a flong is made of the forme as a whole; and a plate of type metal called a stereotype or cliché is cast from the flong and used in turn for printing.

It’s true that all fashioning could itself arguably be broken down into acts of induction in the sense that (say) a painting is a record of brushstrokes, equivalent to footprints as a record of walking.  What allows us to differentiate fashioning from induction here, I think, is the exercise of will over specifics of form.  If I walk around purposefully on the shore of a desert island where I’ve been cast away so that my footprints spell out the words HELP ME, then I will have fashioned that message at the same time I was inducing a record of where I walked.  The distinction lies, perhaps, in a creator’s intention to communicate something, to engage in symbolic behavior.  Or perhaps it lies instead in our intention as readers, viewers, or whatever: whether we’re interested in the purposeful message HELP ME or in fortuitous data about where a castaway has been walking—though, in that particular case, the one can’t be well understood in isolation from the other.

In this regard, it may be informative (and important) to think about how aleatory forms fit into the scheme I’ve been constructing here—that is, forms whose details are understood as deriving not from preexisting forms, as with impressions made from a leaf or a printing plate, but from chance elements.  Take, for example, the art of marbling, in which colors are floated on a liquid, allowed to assume complex patterns that are guided but not tightly controlled, and then transferred to paper or some comparable surface.  Or consider the mechanism that governs the notes played by an Aeolian harp or a wind chime.  These cases too, I believe, fall under the rubric of induction.  Indeed, the practices of allowing light to fall on a photosensitive plate or aerial vibrations to jostle a membrane are not so very ontologically different.  What these practices share in common with each other is their surrender of formal detail to external factors, whether those factors are classified as “nature” or “chance” or something akin to the patterns on a seal-ring.  And what those factors are external to is the set of conscious and purposeful acts that serve to bring any particular object or event into being—that is, a particular token or manifestation or iteration, such as an impression of a seal, a photographic negative, a physical painting on canvas, or a wind chime “performance,” and not something more abstract, such as a “work.”

I proposed above that we distinguish between fortuitous and premeditated inducenda.  But what kind of inducendum is a person purposefully posing for a photograph?  On one hand, the person himself or herself is a fortuitous inducendum: he or she presumably did not come into being for the purpose of being photographed (although we might not be sure about this in the case of certain celebrity children).  But the person’s pose is another matter, since it was struck for purposes of induction; this is what we might call a “photogenic” behavior.  By the same token, the prehistoric human hands used as stencils in cave painting were themselves fortuitous inducenda, but the pressing of those hands outstretched in specific awkward-to-reach places was—what?  Cave-painting-ogenic behavior?  The particular configuration of fingers in such hand stencils has also been explored for potential “symbolic intentionality” in terms of finger-counting; see the work of Karenleigh Overmann.  At issue here are all those behaviors that consciously aim to produce an effect suitable for transfer into a medium, whether with one’s own body or with other implements, but that do not themselves create the fixed objects or transient signals which they’re undertaken to support; that is, one must still arrange somehow to fix, transfer, or transmit the target effect.  I sense a strong continuity between these behaviors and certain other ones: posing for paintings, drawings, and the like, or setting up a still life for painting rather than photographing.  These latter examples are not inducenda because they are subject to a process of fashioning rather than induction.  But they entail such similar behavior and motives that I’m inclined to think of them as part of the same category: they too aim to produce an effect capable of transfer into a medium, except that the transfer in this case requires fashioning.  Granted, setting up a still life could be regarded as fashioning in its own right, and so, I suppose, could posing, if one accepts one’s own body as a material one can fashion through movement (as in dancing, as opposed to piercing or tattooing).  But the relationship between the fashioned object (e.g., vase of flowers) and the target object (e.g., photographic still life, painted still life, television signal with view of flowers) seems rather indirect compared to, say, the relationship between a seal-ring and one of its impressions.  The target object in this case is not a facsimile of the fashioned object, but instead represents a perspective on the fashioned object.

Perhaps the most productive way of thinking about this is to imagine tracing and fashioning in terms of a continuum—one in which we can distinguish drawing a vase of flowers “from life” from drawing a vase of flowers “from imagination.”  The former comes closer to tracing, though not as close as tracing a shadow cast on a wall by the same flowers would be; the latter is further away from it.  And tracing, in turn, with its lesser demand for skills of subjective observation, comes closer to induction, which requires no skills of subjective observation at all.  Within this framework, the setting up of subjects or models can be functionally advantageous anywhere short of art from pure imagination, and it serves a consistent purpose in contriving desired subject matter.  The artist who holds out her thumb and squints as a means of measuring scale is reifying and harnessing a field of vision in a way that arguably differs from the use of a camera obscura or camera lucida only in degree.

This business of setting up subjects or models plainly transcends the induction/fashioning divide, spanning a very broad range of activities that nevertheless all share something fundamental in common.  That something is not a distinctive set of formal characteristics, even though it may have formal ramifications: virtually any type of creativity, whether performance creativity or product creativity, is eligible.  It is, exclusively, a matter of purpose: to create an effect for initial transfer into a medium.  This may be complete (a pose for the camera, a studio recording session, a setting-up of a still life) or partial (a live event that is incidentally televised, and is therefore programmed in such a way as to leave time for commercial breaks; a ceremonial ribbon-cutting that has, as just one of its objectives, the securing of a photograph for the newspapers).  If we include light and air (as a medium of sound waves) in our understanding here of “medium,” and allow that the actions might sometimes be sufficient in themselves to transmit a signal through that medium (I speak; you hear), then this category becomes extraordinarily broad.   I’m not sure we want to go there, but even if we did, that would still be okay; my point here is less to draw a line around the activities I’m describing as a whole than it is to identify a distinctive kind of relationship which given activities can have with respect to given media.

And, ideally, to name it as well, for sake of convenience.  So let’s call it genic activity, generalizing from such terms as photogenic, phonogenic, cinematogenic, and telegenic (following the model of generalizing, say, etic/emic from phonetic/phonemic).  It’s true that biologists already use genic to mean “of, pertaining to, resembling, or arising from a gene or genes,” but the combining form -genic is associated with “pertaining to suitability for reproduction by a medium” (both quoted definitions are lifted from http://www.dictionary.com/browse/genic).  I suppose people can have inherently genic qualities (a “good telephone voice”), which is how this matter usually gets talked about, but I prefer to associate the genic with things people do rather than simply with what they are.  We might also speak of geny (genic activity in the abstract) and genicity (the quality of being genic); and perhaps we can even speak of people gening the subjects of still lives (by arranging flowers, fruits, etc.) or themselves for portraits (by striking poses).  I visited the photographer and gened a picture for you.  How did I do?  And could we possibly even refer to the genic subject, prior to its transfer into a medium, as a gene?  To associated practices as genetic?  For that matter, are there productive analogies or continuities to be explored between biological genetics and media genetics?  Or would the whole scheme fall apart if we tried to harmonize these two things?

Is DNA the stuff of fashioning or induction?


Retroduction, as I stated earlier, occurs when content is induced and then educed in turn to generate sensory stimuli that meaningfully resemble those associated with the “original.”  The resemblance may be partial, or it may be effectively complete, lacking only in Benjaminian aura.  But it is emphatically a resemblance between sensory stimuli (the educta), and not between the physical objects or systems from with those stimuli are brought out (the educenda).  There is little similarity between the physical structure of a person’s face and the physical structure of a photograph of that face.  But there is a resemblance between the patterns of photons which the two will yield with respect to a particular vantage point.  The “copy,” if you will, can be called a retroduct.  But by that I don’t mean the photograph as a flat object; I mean an educed pattern of light that resembles an “original” pattern of light.

The discovery of suitable retroducta is a separate matter from the discovery of methods of inscription per se.  Consider the reason Samuel F. B. Morse gave for discontinuing his early experiments in photography in a letter of March 9, 1839:

I don’t know if you recollect some experiments of mine at New Haven, many years ago, when I had my painting room next to Prof. Silliman’s, experiments to ascertain if it were possible to fix the image of the Camera Obscura.  I was able to produce different degrees of shade on paper, dipped into a solution of nitrate of silver, by means of different degrees of light; but finding that light produced dark, and dark light, I presumed the production of a true image to be impracticable, and gave up the attempt.

It was the good fortune of the daguerreotype that, viewed from a position perpendicular to its surface, it happened to present a retroduct in which dark was mapped to dark and light was mapped to light (for technical reasons at the microscopic level that were not appreciated until well into the twentieth century).  If it had been the other way around—as it is, in fact, if you view a daguerreotype from a different angle—photography might have had to wait a few more years to gain traction.  Subsequent photographic processes such as the collodion positive or “ambrotype” were less about tangible fixation than they were about strategies for obtaining a retroduct with its range of brightness uninverted.

Now let’s consider time-variant retroduction (colloquially “playback”).  This occurs when an “original” is induced as it unfolds over time, and the result is educed over time in turn, such that the resemblance in sensory stimuli encompasses the aspect of time: the rhythm of a Morse code transmission, the sound of a voice, the sight of a horse galloping.  Time-variant retroduction includes phenomena such as telephone transmissions where the content is evanescent and input time is effectively identical to output time.  But one of its subcategories is time-based retroduction, defined by the presence of time transduction: time is induced into some other modality, such as linear space, and then educed from that other modality back into time.  The time base is the representation of time in that other modality.

Time-variant induction, by itself, doesn’t imply any iconicity with respect to the time aspect.  Think of a seismograph that draws earth tremors on paper: the wavy line doesn’t resemble the tremors either in its physical form or in the visible educt we see when we look at it as a static image.  Or, rather, it doesn’t resemble them within the framework of a three-dimensional system of spatial coordinates.  If we accept time as a fourth spatial dimension, then the line could perhaps follow the physical contour of the ground’s surface (or at least of the recording stylus) in that fourth dimension.  But since we can’t see into the fourth dimension, such a resemblance would still not be apparent to human observers, except in terms of reasoned analogy.  The static time base is really a convention, albeit a very old one, dating back to tally sticks in which the time-based activity of counting was mapped to a linear spatial axis, and from thence to the writing of language as sequences of words or sounds.

A time-variant likeness instead arises only when we add time-variant eduction with its changing patterns of light, its time-variable patterns of air pressure, and so on.  The educed sensory stimuli can then vary recognizably over time as the “original” sensory stimuli did.  What comes across is what it’s like to hear a given voice, or what it’s like to see a horse gallop, or what it’s like to experience a waltz rhythm.  Perceptually, this is a matter of triggering or invoking time-variant gestalts or time-variant qualia, which is what I believe we mean when we speak of time-based media “bringing things to life” in ways that other media don’t or can’t.  Thus, we perceive middle C as sound, and don’t analyze it as 261.6 vibrations per second (as we might by studying a waveform on paper); and we perceive a horse galloping as movement, and don’t analyze it as a sequence of discrete hoof-positions (as we might by studying the images laid out side by side in a grid).  Time-variant retroduction (or time-variant eduction more generally) exploits distinctive sensory capacities that other forms of eduction do not, and it thereby enables us to grasp subjects in different—and differently informative—ways.  This is the same principle that made the blink comparator useful for astronomers (switching rapidly between two photographs of the night sky to look for objects that changed position), and while it relies on sensory experience, its value isn’t limited to providing experiences as such.  After all, the blink comparator was used to discover Pluto, and not just to give viewers a subjective feel of the night sky.  By the same token, there’s nothing inherently soft or fuzzy about the insights we stand to gain from “playing back” historical time-based media, notwithstanding the rhetoric into which proponents of its preservation habitually fall.  Not that there’s anything wrong with pitching the delights of time travel; that talk just fails to present the whole picture.

Time-variant retroduction is usually audiovisual, which is to say it deals in audio, video, or both simultaneously and in sync.  But it can take other forms as well.  Imagine a record of the human pulse “played back” as variations on the pressure of liquid in a flexible tube that can be palpated like a real artery, to comparable sensory effect: press your fingers against the mannequin’s arm and feel the recorded pulse of a man born in the year 1769.  Or imagine weather data being “played back” over time in an enclosed space through the exertion of artificial control over its temperature and humidity: put your hand through the slit in the plastic and feel the weather recorded exactly one hundred years ago on this day, at this time, in this place.

On the other hand, much as retroduction can ignore the aspect of time while preserving a subject’s other attributes (as happens with a still photograph), so it can also abstract rhythms or movements from their original trappings—for instance, if we retroduce the percussive tapping of a telegraph key as the beep of a 1000 Hz oscillator, or if we use motion capture to animate digital character models, or if we use a radio receiver to listen to natural radio waves as audible “whistlers.”  The retroduction of a piano performance on a so-called reproducing piano falls somewhere in the middle: the timing, notes, and type of instrument are all “correct,” but relayed to a different piano with its own unique timbre.  Monochrome photography has its own obvious “deficiencies” which carry over into monochrome films: we can retroduce patterns of light waves relative to a flat surface in terms of amplitude (brightness) but not frequency (color); or, if we think in terms of photons, in terms of quantity but not energy.  Indeed, retroduction is always limited in some way, since we can never rephenomenalize all aspects of a past reality any more than we can step twice in the same stream.  And it is therefore always selective: we choose which parameters to retroduce and which to eschew from among the technically available options depending on what we deem to be meaningful or desirable.  Is color important?  How about stereophony or stereoscopy?  And how exactly do we adhere to original scales—do we boost or reduce volume or contrast, or do we compress or expand time?

The principle of time-based retroduction has yet to have its history written, in spite of how important it seems to be for understanding the roots of modernity.  Early spheres of application included keyboard music, telegraphy, motion photography, and sound recording, and these trajectories doubtless influenced and reinforced each other somehow, but it’s unclear at present how that interrelation actually played out, or why things took off when they did.  To the best of my knowledge, though, the basic idea was first suggested (in an isolated case, centuries before it would gain serious traction) by the Banū Mūsā brothers of ninth-century Baghdad in the context of recording the motions of the fingers of a musician playing an organ on a rotating wax drum, using the marks in the wax as a guide to pinning a barrel, and then using the pinned barrel as a program for a mechanical musical instrument.  The original Arabic text of their account was published in Al-Mashriq in 1906, transcribed from an apparently unique manuscript in the library of—if I’ve identified it correctly—the Ecole des Trois Docteurs in Beirut.  It has also been translated into English by George Farmer and into German by Eilhard Wiedemann (here, starting at p. 169).  A good critical edition of this text, with a more fluent English translation, would make for a worthy project.

It’s true that one step in the Banū Mūsā brothers’ scheme would have involved the kind of intervention I’ve proposed we call tracing: using the wax record as a guide for the manual placement of teeth.  But here we might also distinguish between time-variant and time-invariant tracing.  As a point of contrast, consider someone tracing the rhythm of a piece of recorded music by listening to it and pressing a key in time with the beats.  The tracing would then be dependent on the listener’s accuracy of perception and response over time: we can imagine her getting caught up in the rhythm, anticipating it, inferring it, and so on.  But in the Banū Mūsā case, the tracing would be time-invariant, based on the spatial lengths and positions of marks in the wax—a perception of patterns quite different from that involved in listening to music.  We might get some mistakes, but they would be mistakes of a kind wholly unlike that of our key-tapping listener getting swept up in the feel of the rhythm.  Or consider an analogous case covered previously at Griffonage-Dot-Com: on June 1, 1639, Johannes Hevelius observed a solar eclipse at Gdańsk using a telescope attached to a camera obscura and traced the occultation, as projected onto a flat surface, at regular intervals to produce an image sequence.

Hevelius would have traced each of these individual contours by hand based on what he saw projected by the camera obscura.  However, the form of the change over time was captured not through his direct observation of it as change, but rather through differences between his observations.

The motion we see by animating the Hevelius sequence—as a time-lapse video, with accelerated time base—is scarcely something he could have imposed subjectively on the data he was inscribing.  It’s more objective, I’d argue, for having been traced outside its native modality.  It may not be retroduction, strictly speaking, but I also feel that it approaches retroduction by virtue of its lack of conscious human input.  The source of its time-variant resemblance certainly seems more closely akin to retroduction than it does to the kind of fashioning associated with designing picture sequences for early optical illusion devices such as the phenakistoscope.

The distinctions I drew earlier among categories of inducta (fortutious, premeditated, natural, artificial) pertain to time-variant inducta as well.  We can, for example, speak of natural time-variant inducta such as sedimentary rock strata or trace fossils, both of which may have loosely recoverable time bases.  But a time-variant aspect can also be fortuitous even when the constituent inducta are premeditated.  Think of the stele rubbings described by Wu Hung, which were individually contrived to be time-invariant copies of the stele, but which taken together comprise a fortuitous time-variant record of the stele’s deterioration that could conceivably be presented as a time-lapse moving picture.  In such situations, we can sometimes cobble together time-based retroductions even where no intentional time-based “recordings” exist.

There are also time-variant genic behaviors, which are worth distinguishing from the time-invariant sort.  In one sense, dictating to a stenographer is like posing for a painting (contriving subject matter for fashioning), while dictating to a phonograph is like posing for a camera (contriving subject matter for induction).  But the dictation in either case is also time-variant, while the poses are time-invariant.  Subject matter of the second kind is “set up” and then simply held in place while inscription occurs.  By contrast, subject matter of the first kind unfolds dynamically over time, often requiring a skill set more like that of performance creativity than of product creativity.  Much as “playback” presents phenomena that we perceive non-analytically as gestalts of movement or sound, time-variant genic behaviors consist of actions that we enact non-analytically over time as gestalts of movement or sound with formal complexities of which we’re not fully aware—think tones of voice, gestures.  Therein lies much of the power of time-variant media to enthrall and persuade.  But the same kind of emergent genic “performance” might date back to Homer, as an oral Singer of Tales, speaking his winged words to whoever wrote them down.

If we concede that air and light count as “media” in this context—again, I’m not sure we want to go there, but maybe we do—then we would also need to concede that they’re time-variant media, capable of bearing time-variant signals.  Even “ordinary” speech could then arguably be considered genic with respect to the air, and liable to be adapted to specific exigencies of that medium, whether I whisper intimately in your ear or halloo to you across a ravine.  Similarly, a “live” stage play might be considered just as genic as anything that goes on in a television studio if analyzed strictly in terms of its sensory components and the physicality of their transmission to an audience via light and compression waves.  From this point of view, what would be distinctive about the genic behaviors associated with phonography, television, and so on would be not genicity per se, but only genicity with respect to those specific media.


So there you have a second batch of my thoughts about what an eductionist approach to media studies might look like.  It has no grand conclusion; just an abrupt end.

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