dynamics, such that they need to be considered in philosophy of science. INTRODUCTION Although most popular books on nanotechnology are about futuristic visions, they also provide a stereotypical account of its history that is strikingly focused on images. 1 Of course, no book forgets to mention Richard Feynman 9s 1959 dinner speech in which he outlined the theoretical possibilities of what is nowadays called nanotechnology.<br><br> However, the Nrst real episode in nanotechnology begins in 1981, when the IBM physicists Gerd Binnig and Heinrich Rohrer invented the Foundations of Chemistry (2006) 8: 53 372 Ó Springer 2006 DOI 10.1007/s10698-005-3358-5 scanning tunneling microscope (STM) to image individual atoms. Five years later, Binnig and others developed the atomic force microscope (AFM) that allowed manipulating individual atoms on surfaces under visual control. In 1990, the IBM employees Don Eigler and Erhard Schweizer used the device to 8 8write 9 9 IBM 9s logo with pointy bright-blue xenon atoms on a smooth dark-gray nickel surface.<br><br> After its publication in Nature and worldwide dissemination, the image became visually compelling evidence of the human capacity to manipulate the world 8 8atom-by-atom 9 9 and to build various molecular devices in the future, including 8 8assemblers 9 9 that Eric Drexler had eloquently described in 1986 in his mechanical engineering vi- sion of doing chemical synthesis which he called nanotechnol- ogy (Drexler, 1986). The 8 8standard story 9 9, which is currently criticized by his- torians and philosophers of science, 2 is interesting because it features images as rhetorical tools for making nanotechnolog- ical visions plausible to a broader public. Authors employ images like epistemological arguments in order to convince readers of certain feasibility hypotheses and thus try to inspire and direct future research.<br><br> While an analysis of the use of images in the 8 8standard story 9 9 provides insight in the propa- gation and rhetoric of visionary nanotechnology, it does not tell us much about the role of images in the actual research in molecular nanotechnology. In this paper I argue that images play an important role in the actual research as well. In order to do so, it is important to distinguish visionary nanotechnology and its 8 8standard history 9 9 from actual research and to replace rhetorical analysis of the propagation of nanotechnology by aesthetic analysis of the images that researchers have actually used.<br><br> If molecular nanotechnology is distinguished from other Nelds of research, including research in nanoparticles, nanocomposites, micro-electro-mechanical systems, scanning probe microscopy, etc., then it is by the speciNc goal of building molecular devices or 8 8machines 9 9. Many other Nelds are concerned with molecular devices, including molecular biology and electrical engineering. However, the only advanced re- search in building molecular devices has been in supramolecular 54 JOACHIM SCHUMMER chemistry since the 1970s, if not earlier.<br><br> 3 Thus, if we want to understand what actual research in molecular nanotechnology has been achieved, as opposed to visions of future nanotech- nology, we need to deal with supramolecular chemistry. Today, this Neld is well established, with many journals, handbooks, and textbooks. 4 It is also quite productive in producing hun- dreds of molecular devices.<br><br> Compared to visionary nanotech- nology, however, the actually accomplished devices are very simple tools, and they are produced by methods that take advantage of two centuries of chemical synthesis rather than from drawing analogies from mechanical engineering. The history of supramolecular chemistry still needs to be written. Of course, there are many historical accounts by its leaders or 8 8founding fathers 9 9.<br><br> However, the diversity of such personal narratives, as well as the diversity of the authors 9 backgrounds, suggest that the history has been quite intricate. Besides the impact of the general Neld of colloid chemistry, it is certain, however, that biochemistry had a particularly strong impact on the development of supramolecular chemistry. En- zymes or complexes of enzymes, with their astounding perfor- mance of accelerating and thus guiding intracellular chemical reactions, were the Nrst complex systems with biologically framed functions whose mechanism was studied and explained chemically.<br><br> In the 1970s, Jean-Marie Lehn, one of the founders of the Neld, originally started by investigating the transport mechanisms for cations (potassium and sodium ions) through nerve cell membranes, and thus investigated supramolecular systems that perform quasi-mechanical functions (transporta- tion) within a larger biological system (Lehn, 1988, 1995). Also, the biochemical understanding of the molecular mechanisms of myosin that makes muscles contract 3 the primary biological motor, so to speak 3 has had some impact since the 1970s. 5 In this paper, I do not provide a disciplinary history of supramolecular chemistry, 6 but focus on the aesthetics of sci- entiNc images from the Neld.<br><br> I argue that the molecular device approach of supramolecular chemistry emerged from chemistry by way of a gestalt switch that enabled a new way of perceiving and interpreting molecular images. The visual fascination with certain images, a thoroughly aesthetic phenomenon, prompted 55 GESTALT SWITCH IN MOLECULAR IMAGE PERCEPTION and motivated research in molecular devices. After providing a brief introduction to supramolecular chemistry as opposed to molecular chemistry (Section 2), I discuss some of the fasci- nating images of molecules that 8look 9 like ordinary objects (Section 3).<br><br> In Section 4, I take the paradigmatic case of catenanes to analyze the di erent forms of representations of supramolecular systems. Section 5 focuses on the new techno- morph sign language of supramolecular chemistry and its combined use with structural formulas as a semiotic, strategy to resolve the gestalt switch. In Section 6, I employ the semiotic theory of aesthetics by Umberto Eco for a better understanding of the aesthetic phenomenon and its resultant research dynamics.<br><br> More generally, I argue that philosophy of science need to be broadened to include aesthetics if we want to understand the dynamics of scientiNc research. MOLECULAR VERSUS SUPRAMOLECULAR CHEMISTRY Molecular chemistry describes the chemical constituents of substances in terms of single molecules. While a molecular approach is useless for substances like metals, salts, and even water for many problems, it has been very successful in most of organic and much of inorganic chemistry for the past two centuries.<br><br> In this models approach, a pure substance consists of a single sort of molecules loosely associated to each other in a condensed phase, while a mixture of two or more substances consists of two or more sorts of molecules equally distributed and again only loosely associated to each other in condensed phase. At the heart of this model is the assumption that one can clearly distinguish between the association of atoms within a molecule, called covalent bonds, and various kinds of weaker associations between atoms of di erent molecules, such as van der Waals forces and hydrogen bonds. While molecular chemists usually do not much care about intermolecular asso- ciations, unless they play a role in the course of a chemical reaction, supramolecular chemists have made it the focus of their study.<br><br> Thus, according to a frequently repeated standard deNnition by one of its founders, Jean-Marie Lehn, supramo- 56 JOACHIM SCHUMMER lecular chemistry deals with intermolecular forces as opposed to molecular chemistry that deals only with intramolecular forces (see Table I). There is something missing in this deNnition, however. 7 Not only do supramolecular chemists obviously deal with both in- termolecular and intramolecular forces, but also many other Nelds have long dealt before with intermolecular forces, such as chemical kinetics, catalysis, organometallic chemistry, much of physical chemistry and condensed matter physics, polymer chemistry, colloid chemistry, biochemistry, molecular biology, and so on.<br><br> What is missing in the mentioned deNnition of supramolecular chemistry is a particular functional perspective. Indeed, supramolecular chemistry deals with the associations of two or more molecules only insofar as they constitute a system that can perform certain functions. Moreover, being largely a branch of synthetic chemistry, it is not only about under- standing functions, as in molecular biology, but also about creating new systems that perform certain functions; that is, supramolecular chemistry is about creating supramolecular devices.<br><br> Since these devices consist of several molecules and thus span a nanometer and more, supramolecular chemistry is the current scientiNc manifestation of what visionaries of molecular nanotechnology have conceived of, though they noticed its existence only lately. Still we need to specify the kind of functions that supramo- lecular chemistry is concerned with. It is important to note that, unlikephysics,muchofchemistryandmolecularbiologyisabout functions,which philosophers of science tend to disregard.<br><br> For a chemist, a molecule is a composition of chemical functionalities, i.e. dispositions to react with a certain kind of molecules under certain conditions to form another kind of molecules 3 thus a molecule isbothasubjectandatoolforchemicalstudies. Hence, in standard chemical representations of molecules, in structural formulas,thesmallestgraphicalelementsthatrepresentchemical propertiesarenotatomsbutfunctionalgroups 3groupsofatoms with well-deNned chemical functionalities.<br><br> Supramolecular chemistry is distinguished from that and from the aforemen- tioned Nelds, because it goes beyond the chemical functions of reactants or enzyme complexes. Its goal is to create molecular 57 GESTALT SWITCH IN MOLECULAR IMAGE PERCEPTION TABLEI Molecularversussupramolecularchemistry MolecularchemistrySupramolecularchemistry FocusIndividualmoleculesMulti-molecularsystems Intramolecularforces(covalentbonds)Intermolecularforces(e.g.vanderWalls forces,hydrogenbonds) FeaturedpropertiesChemicalfunctionsMechanical,electrical,electronic,optical,and biologicalfunctions Featured representation systems Structuralformulas(functional groupsandreactionmechanisms) 8 8Technomorphrepresentations 9 9along withstructuralformulas 58 JOACHIM SCHUMMER systems that perform functions other than simple chemical functions, including mechanical, electrical, electronic, optical, and biological functions. Therefore, supramolecular chemistry transcendsnotonlyclassicaldisciplinaryboundaries,butalsothe representationalsystemsformoleculesinchemistry,thechemical sign language that depicts chemical functionalities, as will be discussed in Section 5.<br><br> Before that change, however, there were particular charac- ters of the classical chemical sign language that aesthetically prompted a new way of perceiving molecular images. CHEMISTS 9 FASCINATION WITH MOLECULES THAT 8LOOK 9 LIKE ORDINARY OBJECTS In 1989, the German chemist Fritz Vo ¨ gtle published a book called 8 8Attractive Molecules in Organic Chemistry 9 9 as Part One of what should become the Nrst comprehensive textbook of supramolecularchemistry(Vo ¨ gtle,1989a,b, 1990).(Incidentally, Vo ¨ gtle gave lecture courses on that topic at the University of Bonn beginning in the early 1980s when I was an undergraduate in chemistry there.) The molecules that he considered aestheti- cally attractive or beautiful (see also Vo ¨ gtle et al., 1982) largely fall into two classes: molecules with high degrees of symmetry, like the Platonic bodies, and molecules that 8look 9 like ordinary objects (see Figure 1). 8 It is the second class that is of particular importance here.<br><br> 9 For an aesthetic analysis of that fascination, which Vo ¨ gtle shared with many fellow chemists, we need to restore the fun- damentaldi erencebetweenthingsandrepresentationsofthings and reformulate Vo ¨ gtle 9s aesthetic claim: those images that rep- resent both molecules and ordinary objects are aesthetically attractive. As a Nrst explanation, we may say that the images showninFigure 1areaestheticallyattractivetochemistsbecause they establish a symbolic link between the world of ordinary objects and the chemical world of molecules through their interpretative ambiguity. Of course, chemists believe that ordinary objects consist of molecules, but other than that there was no link between these worlds.<br><br> This is not because of the so-called divide between the 59 GESTALT SWITCH IN MOLECULAR IMAGE PERCEPTION quantum and the classical world, which chemists have indeed successfully bridged for nearly eight decades by semi-classical models and by combining quantum mechanical concepts with classical chemical concepts. Rather, the main di erence be- tween the two worlds is that, for a chemist, the world of mol- ecules is governed by chemical functions and the corresponding reaction mechanisms that determine their manifold structural rearrangements, whereas ordinary objects do not have these properties. In other words, everything what matters from a chemical point of view in molecules, save the bare shape and topology, is just missing in ordinary objects.<br><br> And in turn, molecules lack most, if not all, of the properties and functions of ordinary objects. The images that represent both molecules and ordinary ob- jects were fascinating precisely because they symbolically con- nect these two otherwise disconnected worlds, and thus inspired the imagination of chemists. This is nicely illustrated by two cartoons from 1977 that Vo ¨ gtle half-seriously included in his 1989a textbook (Figure 2).<br><br> 10 Here, human beings are downsized to the scale of molecules (or molecules are scaled-up to the size of humans) so that they, in the Nrst cartoon, walk across a cyclophane molecule and, in the second cartoon, take Figure 1. Molecular images that look like ordinary objects. 60 JOACHIM SCHUMMER benzene molecules like bricks in their hands to build new molecular structures.<br><br> The cartoons 9 joke, that molecules are ordinary objects one can walk across and work with like bricks, expresses a new way to perceive molecular representations. Integrating molecules into the ordinary world made them at Nrst more handy and more familiar, which might be one reason why the language of supramolecular chemistry became so rich in anthropomorphisms, like 8 8molecular recognition 9 9, 8 8guest 3 host chemistry 9 9, and why the teleological notion of 8 8self- organization 9 9 could become so popular. Moreover, it encour- aged new ways of manipulating molecules and thus inspired the synthesis of many new molecules and supramolecular systems whose shape or topology resembled other objects of ordinary life.<br><br> The important point is that, once you conceive of molecules as if they were ordinary objects, and thereby abstract them from their original chemical context, you can imagine these molecules performing all kinds of functions that only ordinary objects use to do. All of a sudden, molecules whose images look like a basket (Figure 1) are supposed to carry things around. Since molecular baskets can be created at deNnite sizes, they are supposed to be quite selective in carrying only molecules or ions of the corresponding size 3 what supra- molecular chemists call 8 8molecular recognition 9 9.<br><br> And mole- cules whose images look like rotors are not only called rotane but also supposed to perform the mechanical function of rotors, once the required mechanical context is created in a multi-molecular system, that is, a molecular wheel on a molecular axis, called rotaxane. Figure 2. Cartoons from Vo ¨ gt1e (1989a, pp.<br><br> 5, 345; modiNed versions from S. Misumi, Nrst published in Chemistry Today , 78 [1977], p. 12, 22).<br><br> 61 GESTALT SWITCH IN MOLECULAR IMAGE PERCEPTION DIFFERENT MOLECULAR REPRESENTATIONS: THE CASE OF CATENANES The forth example of 8 8molecules that look like ordinary ob- jects 9 9 in Figure 1 is catenane, a simple but paradigmatic system of supramolecular chemistry that is worth reOecting on. Catenanes are formed by ring closure reactions, such that two rings are interlocked with one another. Originally a matter of pure chance and very low yield (Schill, 1971), the synthesis is nowadays performed with high yields through the use of molecular templates that precisely direct the molecular process 3 atomic-group by atomic-group 3 which supramolecular chemists call 8 8self-assembly 9 9.<br><br> Catenane is not a molecule but a supramolecular system because the two molecular rings are not connected by chemical bonds but by mere mechanical locking, such that these rings can usually freely rotate 3 a curiosity from the point of view of molecular chemistry. Rather than discussing the chemistry of catenanes, I would like to analyze the various molecular representations that chemists have used to depict the same molecule (Figure 3). The classical chemical representations of molecules are structural formulas that focus on functional groups to depict chemical properties.<br><br> In the structural formula of catenane (Figure 3a) one would need the trained eyes of supramolecular chemists to recognize two interlocked links of a chain. That is even more di cult in the representational form of molecular structures (Figure 3b), as provided by X-ray di raction or quantum- chemical calculation, which focuses on exact geometry but is poor in chemical information (Schummer, 1998). Only if one strips o all the chemical and geometrical information to cap- ture only the basic topological structure of the molecules (Figure 3c), the two interlocked links of a chain become obvi- ous to anybody.<br><br> These topological representations, as well as some stylized structural formulas (Figure 1), became the images of aesthetic attraction and subject to gestalt switches. 11 However, since these images alone are bare of any chemical association, they need to be placed in a chemical context to know that they also represent molecules. Only then do they symbolically bridge the worlds of molecules and ordinary 62 JOACHIM SCHUMMER objects, and thus allow switching back and forth between two ways of perception.<br><br> As was argued in Section 3, the symbolical bridge established by such images fosters the imagination of conveying the func- tionalities of ordinary objects to molecules. Yet, what kind of function can two or more interlocked molecular macrocycles perform? Indeed, at the beginning, catenanes were mere toys, exemplifying the existence of nonchemical, mechanical bonds.<br><br> One can play with the reduced mechanical degree of freedom, but one can hardly lock or enchain anything in the molecular world other than again molecular links of chains 3 but for what purpose? After some playing around, though, chemists recog- nized that some catenanes have preferred and deNnite rota- tional states. Furthermore, by applying electricity, light, or a di erent chemical environment, one can switch between these Figure 3.<br><br> Di erent representations of the same catenane molecule (a, b, and d from Balzani et al., 2000; reproduced with permission from Wiley-VCH). 63 GESTALT SWITCH IN MOLECULAR IMAGE PERCEPTION deNnite states. Thus, the mechanical toy in miniature turns into a supramolecular system, a device for the storage of digital data, for which great economical expectations exist.<br><br> Once chemists recognized this functionality, they depicted catenane in a new way, which I call 8 8technomorph representations 9 9 (Figure 3d). THE TECHNOMORPH SIGN LANGUAGE OF SUPRAMOLECULAR CHEMISTRY Technomorph representations of molecules (see Figures 3d and 4) are inspired by electrical and mechanical devices. If perceived in isolation, nobody would associate them with molecules or even with chemistry.<br><br> They have lost any direct reference to chemical formulas or molecular structures and remind of the macroscopic products of mechanical or electrical engineering, which are objects of ordinary experience. Since the techno- morph sign language is intuitively accessible by everybody, such images have become popular illustrations beyond academia, in popular science magazines and even newspapers. There is no more ambiguity, no more gestalt switch.<br><br> Rather the techno- morph representations seem to depict those imagined ordinary objects that supramolecular chemists formerly saw in their ambiguous representations. Since supramolecular chemists developed the technomorph sign language for their systems in the late 1990s, ambiguous signs like Figure 1c have almost disappeared from publications. The ambiguity has been replaced or resolved by representing the same molecular system by two di erent sign languages side by side (Figure 4).<br><br> On the one hand, there are still the structural formulas of chemistry, which is useful because they represent chemical properties and the systems still need to be synthesized by chemical means. On the other hand, there are the techno- morph representations, stripped o chemical information and looking like ordinary objects, but encoded with the functional- ities that the supramolecular systems are supposed to perform. A closer look at how chemists employ the technomorph sign language reveals three levels of combining it with the language 64 JOACHIM SCHUMMER of structural formulas.<br><br> In Figure 4a, which represents a 8 8molecular gear 9 9 and a 8 8molecular turnstile 9 9, technomorph representations are placed next to structural formulas with an arrow from the left to the right, indicating an asymmetric rela- tion, i.e., that the molecular system is an example of the mechanical/electrical system but not the other way round. Color codes allow identifying the corresponding parts of both systems, and arrows indicate the corresponding mobilities that enable the functionality of the mechanical devices. In Figure 4b, two structural formulas, each corresponding to a technomorph representation, are related to each other by a chemical equation, suggesting that one can through reversible chemical reaction switch between the released and the engaged state of a 8 8molecular brake 9 9.<br><br> Although the double arrow is missing be- tween the two technomorph representations, it is clear that Figure 4b additionally relates chemical processes to mechanical processes. Figure 4c, which represents the formation of pseudorotaxane, combines structural formulas and techno- morph representations in one chemical reaction formula. Rather than illustrating the representational correspondence between structural formulas and technomorph representations as in Figure 4a and 4b, Figure 4c takes both forms of repre- sentation as interchangeable.<br><br> This suggests that supramolecular chemists actually switch back and forth between both forms of representations, depending on whether they are interested in chemical properties or mechanical/electrical properties of their systems. In addition, changing the representational form within the representation of a process as in Figure 4c, from structural formulas to technomorph representations, serves rhetorical purposes, as it suggests the sudden emergence of new types of entities during the process. The ambiguity of the formerly used intermediary signs like those shown in Figure 1 has become productive.<br><br> It prompted the creation of a new sign language that is used side by side or even interchangeable with structural formulas. Instead of switching between two kinds of image perception, chemists now use two interlinked sign languages that are adapted to di erent aspects and purposes of the supramolecular search for new molecular devices. 65 GESTALT SWITCH IN MOLECULAR IMAGE PERCEPTION ECO 9S SEMIOTIC THEORY OF AESTHETIC PERCEPTION Thus far I have argued that supramolecular chemistry was essentially inspired by an aesthetic phenomenon that symboli- cally linked the world of molecules and the world of ordinary objects, and that eventually prompted the creation of a new sign language for representing supramolecular devices.<br><br> In this section, I will apply a semiotic theory of aesthetics to provide a deeper insight into the aesthetic dimension of chemical research dynamics. Starting in the early 1960s, the famous Italian novelist Umberto Eco, whose has been a professor of semiotics at the University of Bologna since 1971, developed one of the most important aesthetic theories of the 20th century (Eco, 1962, 1968, 1976). Originally composed for the aesthetic perception of literature, it can be applied to many other Nelds, including an understanding of the chemists 9 fascination with molecular images that look like representations of ordinary objects.<br><br> According to Eco, there are four traits of the aesthetic Figure 4 Examples of technomorph representations along with structural formulas: (a) 8 8molecular gear 9 9 and 8 8molecular turnstile 9 9; (b) 8 8molecular brake 9 9 released and engaged; (c) formation of pseudorotaxane (all images from Balzani et al., 2000; reproduced with permission from Wiley-VCH). 66 JOACHIM SCHUMMER perception of signs (Table II) 3 a sign is, in general, the object of perception, which can be a piece of literature, a painting, or, in our case, a molecular image. (1) Ambiguity of interpretation .<br><br> The signs must be ambiguous in that they allow at least two possible interpretations that cannot be easily reconciled, thus generating a tension in the mind of the interpreter. In the case of supramolecular chemis- try, images of the kind presented in Figure 1 are ambiguous because they can be read as representing either molecules or ordinary objects. The tension, and the fascination with these images, arise because both molecules and ordinary objects belong to rather disconnected worlds that are only symbolically linked by the signs.<br><br> (2) Productive stimulation . The interpreter of the signs is continuously challenged to develop new interpretations in order to lower the tension. In our case, chemists were prompted to bridge the gap between the molecular and the ordinary world.<br><br> They did so not only by humoristic cartoons that integrate one world into the other (Figure 2), but also by reproducing an ordinary world in miniature through the chemical synthesis of ever more molecules that look like and that are supposed to perform functions of ordinary objects, which contributed to the establishment of supramolecular chemistry. (3) Autore;exivity of signs . The interpretation of the signs redirects the interpreter 9s attention from possible denotations towards reOecting on the form of the signs as another approach to lower the tension.<br><br> Here, it prompted chemists to reOect on the structure of their own sign language (Figure 3), and Nnally led to the creation of the technomorph sign language, such that the ambiguity of the original signs were replaced with two interchangeable representations put side by side (Figure 4). (4) Re;exivity of the interpreter . In Eco 9s theory of the 8open artwork 9, the interpreter 9s continuous e ort to develop new interpretations ultimately reveals more about the interpreter than about the signs, because the signs function like a projec- tion plane or mirror on which the interpreter projects his or her own ideas and imaginations.<br><br> This trait of the aesthetic per- ception of signs is not easy to identify in supramolecular chemistry. However, if, according to the main thesis of this 67 GESTALT SWITCH IN MOLECULAR IMAGE PERCEPTION TABLEII FourtraitsoftheaestheticperceptionofsignsaccordingtoEco(1962,1968,1976) TraitDescriptionEvidenceinsupramolecularchemistry AmbiguityCreatesatensionbetween di erentpossibleinterpretations Imagesthatrepresentbothmoleculesand ordinaryobjects Productive stimulation Promptstheinterpretertodevelop newinterpretationsinordertolowerthetension Promptedchemiststobridgethegapbetween themolecularandtheordinaryworld,by reproducingtheordinaryworldinminiature AutoreOexivityRedirectstheattentiontowardstheformofsignsChemistsreOectedonthestructureoftheir ownsignlanguage,Nnallydevelopinganew signlanguage ReOexivityOpenprocessofgeneratingnewinterpretationsthat aretellingabouttheinterpreterrather thanaboutthesigns Producingevermoremoleculesandtheir imagesthataretellingaboutthechemists 9 technologicalmotivationandimagination 68 JOACHIM SCHUMMER paper, the synthetic e orts by supramolecular chemists had originally been triggered by the aesthetic phenomenon, then the synthetic activity is part of the interpretative e orts. It turns out that the ordinary world that supramolecular chemists are trying to reproduce on the nanoscale is a world largely conNned to mechanical, electrical, and optical devices.<br><br> If we take that as the mirror image of the imaginations of supramolecular chemists, it reveals a profound technological attitude, the world of homo faber . In sum, Eco 9s theory allows us to understand not only the aesthetic phenomenon of the chemists 9 fascination with certain images, but also the aesthetic motivation for the development of supramolecular chemistry and the technomorph sign lan- guage. It provides insight into the researchers 9 own and otherwise hidden motivation and worldview, beyond and be- fore the current nano hype.<br><br> The aesthetic analysis suggests that current scientiNc research is indeed largely driven by techno- logical imaginations rather than by understanding the ordinary or molecular world as it is. CONCLUSION It is broadly acknowledged that images perform di erent functions in science. They can be used as illustrations for educational, rhetorical, or communication purposes, they can store information in a very e cient manner, and so on.<br><br> What is largely overlooked, however, is the role that the perception and interpretation of images can play in guiding scientiNc research. In this case study on the aesthetic origin of supramolecular chemistry, I have tried to point out that the perception and interpretation of scientiNc images can play a pivotal role in inspiring and guiding new research Nelds, and that, unlike the received philosophy of science, aesthetic theory can help us to understand the dynamics of scientiNc research in such cases. 69 GESTALT SWITCH IN MOLECULAR IMAGE PERCEPTION NOTES 1 For an analysis of the most popular 34 books on nanotechnology, see Schummer (2005).<br><br> 2 See Baird et al. (2004, part 3); particularly Mody (2004), Hessenbruch (2004), and Baird and Shew (2004). 3 For a recent comprehensive textbook on molecular devices, see Balzani et al.<br><br> (2003), see also the special issue on 8 8Molecular Machines 9 9 of Accounts of Chemical Research 34(6), 2001. 4 The journals in the Neld also illustrate the intricate history of its emer- gence. Journals have included Journal of Supramolecular Structure (since 1972, renamed Journal of Supramolecular Structure and Cellular Bio- chemistry in1981,and JournalofCellularBiochemistry in1982), Journalof InclusionPhenomena (since1983,renamed JournalofInclusionPhenomena and Molecular Recognition in Chemistry in 1989 and Journal of Inclusion Phenomena and Macrocyclic Chemistry in 1999), Supramolecular Chem- istry (since 1992), Journal of Supramolecular Chemistry (2001 32002), Materials Science and Engineering C: Biomimetic and Supramolecular Systems which in 1999 combined Supramolecular Science (since 1994) and Materials Science and Engineering, C: Biomimetic Materials, Sensors and Systems (since 1993).<br><br> Apart from numerous textbooks, several multi- volume works or book series have been published, including Monographs in Supramolecular Chemistry (since 1989), Perspectives in Supramolecular Chemistry (since 1994), Comprehensive Supramolecular Chemistry (11 vols. in 1996), Molecular and Supramolecular Photochemistry (since 1997), and Encyclopedia of Supramolecular Chemistry (2004). 5 For a personal historical account, see Lowey (2003).<br><br> 6 For a Nrst approach to the history of supramolecular chemistry, see Schummer (unpublished). 7 The other problem being of course that the distinction between inter- molecular and intramolecular forces is blurred and mostly historically founded, such that, for instance, organometallic complexes are some- times considered molecules and sometimes supramolecular systems. For a discussion of some further deNnitional problems, though not always with desired clarity, see Balzani et al.<br><br> (2003, p. 7.) 8 For more examples, see Vo ¨ gtle (1989a). 9 For the aesthetics of symmetrical molecules, see Schummer (1995, 2003).<br><br> 10 Vo ¨ gtle acknowledges that his cartoons are modiNed after two cartoons originally published in the Japanese magazine Chemistry Today in 1977 (no. 78, pp. 12, 22).<br><br> 11 Wittgenstein 9s Philosophical Investigations has inspired a philosophical debate over the question if the phenomenon of gestalt switch supports a theory of 8 8plain seeing 9 9 before and independent of any cognitive inter- pretation of the sign. Apart from that debate, I use the term 8 8gestalt switch 9 9 to denote the switch between two interpretations of the same sign 70 JOACHIM SCHUMMER and do not consider further whether the interpretation is an act of 8 8plain seeing 9 9 or cognition. REFERENCES D.<br><br> Baird and A. Shew. 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Nanotechnology and the Negotiation of Novelty.<br><br> In D. Baird, A. Nordmann and J.<br><br> Schummer (Eds.), Discovering the Nanoscale , pp. 135 3145. Amsterdam: IOS Press, 2004.<br><br> J.-M. Lehn. Supramolecular Chemistry - Scope and Perspectives: Molecules, Supermolecules, and Molecular Devices (Nobel Lecture).<br><br> Angewandte Chemie International Edition 27 : 89 3112, 1988. J.M. Lehn.<br><br> Supramolecular Chemistry: Concepts and Perspectives , VCH, 1995. S. Lowey.<br><br> So Near and Yet so Far from Understanding Molecular Motors: Recollections in Honor of John T. Edsall. Biophysical Chemistry 100 : 171 3 175, 2003.<br><br> C. Mody. How Probe Microscopists Became Nanotechnologists.<br><br> In D. Baird, A. Nordmann and J.<br><br> Schummer (Eds.), Discovering the Nanoscale , pp. 119 3133. Amsterdam: IOS Press, 2004.<br><br> G. Schill. Catenanes, Rotaxanes, and Knots , Academic Press, 1971.<br><br> J. Schummer. Ist die Chemie eine scho ¨ ne Kunst: Zum Verha ¨ ltnis von Kunst und Wissenschaft.<br><br> Zeitschrift fu ¨ r A ¨ sthetik and Allgemeine Kunstwissen- schaft 40 : 145 378, 1995. J. Schummer.<br><br> The Chemical Core of Chemistry. I: A Conceptual Approach. Hyle 4 : 129 3162, 1998.<br><br> J. Schummer. Aesthetics of Chemical Products: Materials, Molecules, and Molecular Models.<br><br> Hyle 9 : 73 3104, 2003. 71 GESTALT SWITCH IN MOLECULAR IMAGE PERCEPTION J. Schummer.<br><br> Reading Nano: The Public Interest in Nanotechnology as ReOected in Book Purchase Patterns. Public Understanding of Science 14: 163 3183, 2005. J.<br><br> Schummer. The Twisted History of Supramolecular Chemistry. (Unpublished Paper Presented at the Cain Conference 8 8Nano Before There was Nano: Historical Perspectives on the Constituent Communities of Nanotechnology 9 9, Chemical Heritage Foundation, Philadelphia, PA, 18 319 March 2005).<br><br> F. Vo ¨ gtle. Reizvolle Moleku ¨ le in der Organischen Chemie .<br><br> Stuttgart: Teub- ner, 1989a (Engl. trans. as Fascinating Molecules in Organic Chemistry .<br><br> Chichester: Wiley, 1992). F. Vo ¨ gtle.<br><br> Supramolekulare Chemie . Stuttgart. Teubner, 1989b (Engl.<br><br> trans. as Supramolecular Chemistry , Chichester: Wiley, 1991). F.<br><br> Vo ¨ gtle. Cyclophan-Chemie . Stuttgart: Teubner, 1990 (Engl.<br><br> trans. as Cyclophane Chemistry . Chichester: Wiley, 1993).<br><br> F. Vo ¨ gtle, L. Rossa and W, Bunzel.<br><br> Scho ¨ ne Moleku ¨ le in der organischen Chemie. Kontakte 2: 37 348, 1982 (partly reprinted in: Chemie fu ¨ r Labor und Betrieb 35: 178 3179, 1984). JOACHIM SCHUMMER Department of Philosophy Technical University of Darmstadt Darmstadt, 64283 Germany E-mail: js@hyle.org 72 JOACHIM SCHUMMER<br><br>

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