STABLE KNOWLEDGE?

 
 Rafael Capurro
  
 
 
 
Paper presented at the Workshop: Knowledge for the Future - Wissen für die Zukunft, Brandenburgische Technische Universität Cottbus, Zentrum für Technik und Gesellschaft,  March 19-21, 1997.
A German translation "Beständiges Wissen" was published in the electronic journal LIBREAS (2006).

 

 
Abstract 

How stable can knowledge be? This question is deeply rooted in Western metaphysics. Stable knowledge can be understood in the temporal sense of permanent presence or in the sense of virtual presence, like knowledge in electronic networks. Any kind of knowledge stability (including its signs, meaning, and media) is based on a type of being, ourselves, that has the ability to cast its own being and of being open to the unforeseen. Is the question how stable can knowledge be? as it arises from our present technological cast one that envisages the foreclosure of our ability to cast our being and to remain open to the unforeseen? Should we be committed to technologies that imply this kind of challenge?  


Kurfassung

Wie beständig kann Wissen sein? Diese Frage ist tief in der abendländischen Metaphysik verwurzelt. Beständiges Wissen bedeutet zum einen ständige Anwensenheit, wie zum Beispiel die der Bücher in einer realen Bibliothek, und zum anderen virtuelle Anwesenheit, wie das Wissen in elektronischen Netzwerken. Beständiges Wissen (Zeichen, Bedeutung, Medien) ist aber stets unser Wissen, d.h. das Wissen eines Lebewesens, dessen Existenz gestaltbar und das offen für das Unvorhergesehene ist. Ist die Frage: Wie beständig kann unser Wissen sein? so wie sie aus unserer technologischen Zivilisation entsteht, eine Frage, die diese Dimensionen ausschließt? Sollten wir Technologien verpflichtet sein, die diese Art von Herausforderungen stellen? 
 

 

 
 
 
CONTENTS

Introduction

I. Mythical Prelude    
II. How Stable are Objects of Knowledge?    
III. How Stable are Subjects of Knowledge?    
IV. How Stable are Media of Knowledge    
V. Sustainable Development of Information    

References
 

 
   
  

INTRODUCTION


How stable can knowledge be? The background of this question was suggested to me by Klaus Kornwachs in his invitation to participate in this workshop. It can be summarized as follows. The consequences of our present technological action, particularly in such fields like atomic energy and biotechnology, may be highly dangerous to future generations. In order to communicate them our present knowledge about these dangers we should be able to stabilize it semantically and technologically. Our present situation makes us conscious that communication is not something that comes accidentally to knowledge in addition. 

There is no knowledge in itself but only shared knowledge. Knowledge is always more or less informed (or misinformed), i.e., knowledge is the result of the action by which we can find differences on the basis of what is commonly shared. We are immersed in networks of meaning that we progressively consider as unstable insofar as we find anomalies or differences. While in former times there was a belief in having reached or in the possibility of reaching a stable basis of knowledge - Descartes sought this foundation in the cogito sum -, our epoch believes that there is no absolute ground, and that not only scientific knowledge but also all kinds of socially accepted meaning networks are basically unstable. This belief culminates in a communication system that is basically centered on the ephemeral, i.e., on the task of sharing present knowledge.

This situation leads to the following paradox. Our communication system in its electronic shape is supposed to be on the one hand a universal one, offering a platform for humankind, while on the other hand it makes guaranteeing the transmission to future generations more and more difficult. It stresses the value of the unstable over the stable, of the ephemeral over the durable, of the present over the past and future, of the new over the redundant. But there is no pure communication or pure redundancy, as there is no pure information or pure novelty. Human knowing is an endless process of interpretation, i.e., of finding new knowledge or information, on the basis of seemingly stable networks of meaning.

This leads to the second line of argumentation mentioned by Kornwachs in his letter of invitation. It seems as if we were designing our communication techniques in such a way that the increase of information storage, processing and transmission through electronic capabilities goes hand in hand with a decrease of memory. Plato's story (Phaedr. 274c-275c) about the warning of the Egyptian king, the invention of writing would bring about memory weakness, could now become true for humankind as a whole.

These two lines of argumentation can be summarized by saying that in the first case we are dealing with the question of the stability of the object and/or subject of knowledge, while in the second case we are asking for the stability of the medium. 

How stable are objects of knowledge? My first approach is a metaphysical one and has to do with different kinds of objects as source and guarantee of the stability or instability of their messages. This object-oriented approach can be confronted, secondly, with a subject-oriented or modern view. The question here is how stable is the human messenger? or, in other words, how stable are subjects of knowledge? as a source and target for encoding and decoding messages. This is the field of hermeneutics. Finally, there is the question of how stable a medium of knowledge can be? What does this problem look like under the premises of globalization and computerization and particularly under the present development of short-term memory devices?

The quest for knowledge stability with regard to the effects of our technological action is concerned prima facie with the ethical care for future generations. But, is this care really oriented towards their freedom or are we burdening them to live not only with the technical but also within the semantic constraints of our civilization? The quest for knowledge stability arises out of the unethical effects of our technology and it is therefore only apparently a product of ethical care. How stable can knowledge be? is a question located between the utopia of a pure message that needs no material process or medium in order to be shared, and the distopia of a pure medium, void of any message. In terms of Plato's ontology it is the question about a mediation between pure forms or 'ideas' and the pure medium or chora (Tim. 49ff), a kind of recipient of all kinds of information. Let us first take a look at these metaphysical or object-oriented aspects of knowledge stability. In order to better understand it, I begin with a mythical prelude. 

   
 
 
     
   

I. MYTHICAL PRELUDE


There is one chapter in the history of Western thought that concerns the passage from the vertical structure of the messages (Greek: angelia) of the gods transmitted by poets and priests, to the horizontal structure of logos in the sense of philosophical truth-seeking (Capurro 1996). This by-pass can be interpreted as the search for stable or true knowledge that would reach through dia-logue, i.e., through a critical exchange of logoi, the objects of knowledge instead of being the mediator and receiver of an unstable message based on the uncertain will of the gods. Greek philosophers were truth-seekers. The semantic by-pass from angelia to logos makes explicit this change of perspective. Human logos should discover or un-conceal by itself the stable and/or unstable objects. Un-conceal translates the Greek word for truth (aletheia). Let us briefly analyze the nature of mythical instability in order to understand better its replacement by metaphysical stability.   

Nothing is more uncertain than the will of the gods and more unknowable than fate (moira, tyche). The Moiras are the three daughters of Zeus and Themis, the goddess of justice: One spins the thread of life, it is Klotho; the second one shares life's lot, it is Lachesis; Atropos, the third 'inevitable' one, cuts the thread of life. Nothing is more tragic for the Greeks than our possibility of going beyond the rule of fate without a clear knowledge of what we are doing except if there is a will of transgression (hybris).   

The uncertainty concerning the kind of web being spun by the Moiras starts and culminates with our knowledge of death as a knowledge that gives to all other knowledge a sense of instability and inextricability. Our knowledge of death is a paradoxical one, it is stable and unstable, knowledge and non-knowledge, it belongs to our lifetime and it marks its boundary. Today's inflationary use of web and network metaphors has its mythical counterpart and contradiction in the image of goddesses spinning our life-time. Life design is like wool design: the strings of fortune are interrelated but they have no possibility of their own to master the web as a whole. The main factor, namely time, being something that happens inevitably when spinning but being always beyond the threads themselves and their actual design as a frame of possibilities. Fortune and misfortune are predictable or computable only up to a certain degree. Unpredictability lies within all human knowledge and its transmission.   

 

  
     
  

II. HOW STABLE ARE OBJECTS OF KNOWLEDGE?


The birth of Greek philosophy can be seen as an antidote against the weakness of human life in its dependency on fate and the will of the gods. Plato and Aristotle tried to grasp rationally the difference between our knowledge of the transitory, i.e., of what comes to being and passes by, the transitory and finite things (ta phthora), from our knowledge of a kind of being that always is (aei on).

The Greek conception of a stable being and, correspondingly, of a stable or true knowledge is intimately related to time, durability, and presence. This insight was one of Heidegger's epoch-making keys for reinterpreting Western metaphysics. In his lectures from 1924/25 on Plato and Aristotle he shows that for Aristotle human logos 'dis-covers' truth (aletheia) either by bringing forth the idea or form of the transitory or by grasping what is permanent through episteme (science) and sophia (wisdom) (Heidegger 1992). 

One of the peculiarities of the kind of knowledge Aristotle calls episteme as well as, mutatis mutandis, of techne, i.e., the knowledge of how to make artificial things,is its possibility of being taught or communicated. Scientific knowledge or episteme disposes over the unconcealed, for instance in the case of mathematical axioms, in such a way that it does not need to be permanently facing it (Heidegger 1992: 35-38). This makes a difference to sophia as a permanent and pure sight (theorein) of 'eternal' being. I put 'eternal' in quotation marks because, as Heidegger remarks (Heidegger 1992: 34), the Greek terms aion and aidia should not be identified with the Christian transcendence but refer to a kind of presence that cannot be counted or measured. It is a 'for ever' or sempiternitas and not a transcendent aeternitas

Heidegger stresses that for Aristotle this behavior of permanent standing-by, stable knowledge in the sense of permanent presence facing the permanent, is the highest human possibility but that we cannot fulfill it because our finite existence is dependent on what can be otherwise. This is the reason why for Aristotle the process of consultation between different possibilities of action (praxis) is more relevant for us than the divine behavior of sophia. As things, time, and people are always changing, the process of prudent consultation (phronesis), of weighting alternatives, does not aim at some kind of stable knowledge but looks for a correct decision in a given situation. Such a prudent discourse is originally unstable. Ethics is not possible as a science (episteme) but only as a techne. Sophia, the knowledge of the stable in a permanent and pure sight of it, and phronesis, the knowledge of the unstable, seem to have nothing in common. But, indeed, as Heidegger points out, in both cases we are facing or perceiving something primitive or given (ever-lasting or ever-changing) that is supposed to be unconcealed without logos, originally perceived through pure reason (nous) or through sensual perception (aisthesis). In other words, we must first let things come to an encounter before we start talking about them. These can be, for instance, the facts of a specific situation in the case of prudent discourse or the presupposition that medical care is devoted to cure. At the same time the way of seeing that implies prudent discourse is not a naive perception of what changes, but gets its orientation from sophia as the highest but (during our lifetime) only partially attainable fulfillment of human behavior (eudaimonia).   

Heidegger's interpretation of Plato's Sophistes is concerned with Plato's argumentation in favor of the legitimacy of unstable or sophistic knowledge. Plato's opponent is primarily not the sophist but Parmenides, the defender of the thesis that there is only stable knowledge of what is and no knowledge of what is not, i.e., of what changes. The sophist is the very personification of what changes because he is constantly producing arguments and counter-arguments about everything. In order to show that Parmenides' identification of 'what changes' as 'what is not' is not a feasible one, as it elimantes the fact that there are changing things (produced by nature or by art) as well as knowledge of the changing as personified by the sophists, Plato introduces a new interpretation of being that allows one to say that changing being is, although not in the sense of permanent presence, and correspondingly, that there can be a knowledge of it whose unstable or un-true (wrong, concealing, pretending, disguising,...) status (logos pseudes) depends on its mimetic relation to the ideas. Unstable knowledge is of the kind of true and false given the possibility of a process of a real as well as merely simulated unconcealment. Heidegger conjectures that this late platonic dialogue may have been influenced by Plato's discussions with Aristotle on the concept of potentiality (dynamis).   

How stable can knowledge be? From the viewpoint of Platonic and Aristotelian metaphysics the answer to this question is to be found not in the stability of the knowing subject but in the stability of the possible objects of knowledge. In other words, it is a pre-modern answer. It is the opposite of postmodern instability. But extremes meet. Somewhere in the middle is the modern search for stability of the unstable or historical subject (Descartes, Kant, Hegel).   

In some of his recent contributions (from July 24, 1996) to a World Wide Web discussion group on Heidegger (heidegger@ jefferson.village.virg- inia.edu) Michael Eldred has pointed out that there is a difference between when we address phenomena that are supposed to be in a permanent or constant presence, such as for instance a stockpile of books, and the kind of permanency we conceive of when we talk for instance of a standing committee or of the information rapidly circulating in electronic networks. From this we can draw the distinction between factual or constant and virtual or standing presence. This allows us to see why the ideal of pre-modern knowledge stability comes close to post-modern information instability insofar as in both cases we are dealing with presencing. The stable objects of knowledge as conceived by Plato and Aristotle are offered to us either and mostly in a virtual way, namely as presuppositions of science (episteme), or, seldom, in a constant presence for a wise knower or viewer that cannot remain in this permanent state because he/she is also a doer, i.e., someone who has to choose between possibilities of action. The way electronic information is, is in the mode of a set-up, i.e., as a structure that Heidegger calls Gestell, whose permanent availability is of the type of a virtual presence. But in opposition to the metaphysical objects there is no sempiternal divine permanency behind the Information-Gestell.   

But what is more basic than temporal stability with regard to the Greek concept of presence is, according to Heidegger and to Eldred's interpretation, the concept of delimitation. Presencing means primarily not a virtual or real duration in time but a stable form that allows such duration. It is this delimitation that Plato calls idea and Aristotle morphé. We call it information. It was Carl Friedrich von Weizsäcker who saw very early this connection between the classic philosophic concepts of idea/morphé and the modern concept of information (Weizsäcker 1974: 51; Capurro 1978). Stable knowledge is based on the 'ideal' delimitation of what appears. Ideas are everlasting and stable because they are pure delimitations. They can be unconcealed in a virtual as well as in an actual way. Their presences or absences for a time are only related to the stability or instability of the human knower. It is not the human knower who gives them hold and stance but the fulfillment of their being, that has definitely come to an end or perfection (telos). They are eternal or definitive because their delimitation is a definite one. As a counterpart to this we can say that the stability of information is grounded in its digital delimitation. This ideal delimitation is dependent, as we shall see, on the technological medium.   

 

    
     
  

III. HOW STABLE ARE SUBJECTS OF KNOWLEDGE?


How stable are subjects of knowledge? We have already heard: human existence is basically characterized by its instability. This is true not only with regard to the fact that we are mortal beings, but it concerns our way of being. We conceive ourselves and the things around us under changing or unstable conditions or definitions. Vilém Flusser speaks of human existence as a project instead of a subject, i.e., of something that is subjected to a predetermined plan or rule. According to Flusser, this sense of existential instability constitutes the difference between the search for a stable subjectivity in modernity and our postmodern condition (Flusser 1994).   

But human existence is not pure instability since it is grounded in socio-cultural projects that allow that kind of stability the Greeks called ethos , i.e., a way of living within given norms and traditions. Such ethical projects imply rules as to what is to be considered as real and what not. Such metaphysical rules remain mostly tacit. They are the result of more or less radical changes through long periods of time with complex causations and motivations, producing something similar to what Thomas S. Kuhn has called 'paradigm shifts' or revolutionary changes (in the case of scientific theories).   

In the Internet discussions already mentioned, Michael Eldred has suggested that the English word casting be used instead of 'projecting' when addressing our capacity of creating or, better, 'un-concealing' rules of being. As casting agents of being we have the capacity of constructing or co-structuring different kinds of metaphysical networks that allow us not only to see things but to be ourselves in different ways.   

Modernity looked for some stable structure of the knowing subject, some primordial a priori categories (Kant), according to which we would irrevocably see beings and be ourselves within a stable perspective. This philosophical casting was intimately connected with, for instance, Newton's casting of physical nature. Today's technological casting is no less a product of a long and complex process going back to Plato's ideas, through Leibniz' characteristica universalis, modern symbolic logic, Turing's symbolic machines, etc. that leads to what we can call the electronic or digital casting. Michael Heim has analyzed some of the steps in this history (Heim 1994).   

Echoing Bishop Berkeley's esse is percipi, we can say: esse is computari. This does not mean, of course, that we do not believe in the existence of material things or the like. Esse is computari means that we consider being understood in its being when we are able to cast (and broadcast) it in a digital form. "Bits are bits" and not atoms as Nicholas Negroponte says (Negroponte 1995), but atoms are cast in their being as bits. "Being digital" (Negroponte) is indeed a matter of being in the double sense of this expression: being is a matter of bits and bits are the matter of being. This means, too, that the knower him/herself becomes digital. The question about the stability of the knower has now become the question of the stability of the medium in which bits are. According to Negroponte, all media are digital.   

This digital ontology is nowadays so broad-cast (widespread) that it is mostly taken for granted.

 

 
     
   

IV. HOW STABLE ARE MEDIA OF KNOWLEDGE?


Information is the way reality comes into presence through the digital casting of being. Within this casting reality is a gigantic reservoir of virtual digital presence. Information exists, in contrast to energetic negentropy, in the form of superabundance.   

According to Michael Benedikt 'virtual reality' will not replace but 'displace' some of the objects used for storage and transmission of knowledge to future generations. It will 'cast away' their 'ballast of materiality', as the latest stage in the evolution of Popper's 'World 3' (Benedikt 1994: 4). In other words, the metaphysics of virtual reality is based on digital casting, enabling a new immaterial form of information broadcasting. Plato and cyberspace: extremes meet.   

Truth-seeking metaphysical dialogue replaced the messages (angelia) of the gods as well as the 'sacred stories' (hieros logos) about the mysteries transmitted (paradosis) in oral and/or written form by the priests (Burkert 1990: 58-61). Greek philosophers looked for an ideal stability and for the stability of an ideal medium. This medium was for Plato not the written but the spoken language. This is, particularly since Gutenberg, a strange view! For Plato only the living logos was the adequate medium in which the finest, i.e., stable contents of knowledge (ta timiotera) could and should be transmitted. One reason for Plato's disregard of writing as a stable medium can be found in the disaccordance between the kind of virtual presence provided by the written logos and the eternal presence of the ideas. Only a living logos, i.e., a dia-logue can correspond and co-respond to the pure definitions or ideas. We are able to overcome the difference (dia) or the foreign medium between the knower and the object only logically through living logoi. Due to the immediate presence of the living logos to its logical or ideal object we are not separated by any perishable substance but are united in a common logical form. This is the ideal of Platonic in-formation, i.e., of pure logical medium. This ideal medium is indeed, for Plato, the message. Angelia is logos.   

Modernity replaced this metaphysical casting through the conception of a knowing subject as a stable medium. Information technology transformed the modern subject into an object of in-formation. But this process does not necessarily lead to the domination of information technology over humankind. It also enables the transformation of the modern subject into a project (Flusser). The medium of our projections is digital casting. Within it logos is not primarily oriented toward a stable object, but consists of unstable messages. Angelia displaces logos.   

Information technology is a highly unstable medium, but through it we are immersed in a superabundance of virtual messages. This superabundance creates, on the one hand, a new form of stability. Decentralized network architecture, such as the Internet, provides more stability in case of a breakdown. A brilliant idea - based on military tactics! But within this superabundance we are facing more and more the problem of the gap between the information poor and the information rich (Capurro 1996a).    

How stable is the digital casting of information? Nicholas Negroponte writes in a printed book (!):   

"Digital books never go out of print. They are always there." (Negroponte 1995: 13) 
Are they? Of course they are, if we consider this statement as a metaphysical statement. It proclaims a higher (virtual) stability as the one guaranteed by the material medium of real books. But, indeed, there is neither a pure message nor a pure medium. Both, the medium and the message, are irrevocably related to human casting. Human memory, stones, paper, electronic devices...: behind a technical question concerning the durability of a particular medium we are asking: what does it mean to archive knowledge? The metaphysical question arises out of the existential one.   

Under this perspective we are approaching the problem Jacques Derrida calls "mal d'archive" ('the evil of the archive') (Derrida 1995). According to Derrida the principle of archiving and archiving is, as the word arche itself says, a matter of principle or foundation is at the same time opposed and intimately related to what Sigmund Freud calls the "death-drive" ("Todestrieb"). To archive means, on the one hand, to repel death and oblivion. Archives are instruments of recall, Greek hypomnema. The Greek concept of mneme or storage is complementary to the process of recall or anamnesis. Storage and recall are based on an announcement (angelia) preceding them. Death is, according to Derrida, an anarchical angel destroying the message as well as its archive. But, on the other hand, archives are exposed to destruction by death, the "the evil of the archive". Derrida points out that the classical philosophical concept of science (episteme, theoria) was independent of the question of archiving. Our present technoscience has moved away from this idea. It is basically related to all kinds of archival techniques. Even more: the technical medium determines the structure of what is archivable. The medium is the message. But, indeed, which medium? We are concerned with a plurality of media as well as with a plurality of messages. The media are the messages. We are still lacking a theory of messages which would include a theory of the different kinds of messages in science, mythology, art, etc.   

As Wolfgang Welsch remarks (Welsch 1996: 317) media can be universal, but they are never total. They can include everything, as in the case of our present digital casting, but they can do it only specifically. Each medium has its own specificity. The desire to archive as opposed to oblivion and death, to the "to evil of the archive", has many technical devices but, according to Derrida who interprets Freud (Derrida 1995: 59), it is basically grounded in a genetic as well as cultural transgenerational memory. The question of archiving is a question of our care for future generations. But, indeed, what do we know about the future?   

 

 
     
  

  CONCLUSION: SUSTAINABLE DEVELOPMENT OF INFORMATION


Under the conditions of technoscience we can no longer give the primacy to the classical (Greek) conception of science as an archive-independent transmission. The consequence of this classical conception was the idea of a pure archive, as dreamt by Leibniz in his lingua universalis to be implemented in what we call today a computer. The computer should be, under this perspective, a metaphysical medium.   

When we ask: what is an archive? it is because we are suffering, as Derrida suggests, from the "mal d'archive". Against the infinity of destruction we can oppose only finite messages and specific media. The question of archiving has no final solution but a dissolution in a plurality of media and of what we can call information cultures. Giving up metaphysical ideo-logies does not mean throwing away rationality or logical consistency or even modern technology, but becoming aware of our casting potentialities and of those of future generations.    

Human castings are based on the plurality of languages, on different kinds of communication styles, on religious traditions as one of the oldest prototypes of transgenerational cultural transmission, on historical and political processes, etc. Media instability is simultaneously a threat and an opportunity for future generations to inform themselves within their own castings. We should not try to take away this care for their own castings or, even worse, we should not take them away the possibility of giving up our casting under the threat of their own dissolution! In that case we would create archives of death and our message would be apocalyptic.   

Logoi are true or false - with a lot of possibilities in between. Messages are relevant or irrelevant, also with a lot of possibilities in between. There is no relevance in itself. Messages are relevant according to situations and environments. Metaphysics was interested in disclosing the logical character of messages. A theory of messages (an angeletics) looks for the situational (linguistic, cultural, historical, political...) relevance of logoi. To take care with logoi means not only to become aware of their relative truth or stability but primarily to take care with the instability of their transmission. Recalling this instability within a plurality of objects, projects and media is the task of a sustainable development of information. Sustainable development of information means, in other words, saving for future generations the possibility of different castings of being.   

How stable can knowledge be? Does this question arise from our present technological casting envisaging the foreclosure of our ability to cast our being and to remain open to the unforeseen? Should we be committed to technologies that imply this kind of challenge? An alternative to this perspective is not only the univocity and stability of metaphysics but the plurivocity and instability of objects, projects and media, i.e., the notion of information cultures to be studied on the basis of a theory of messages similar to what Flusser calls "Kommunikologie" (Flusser 1996).   

 

 
     
   
REFERENCES

Benedikt, M. Ed. (1994). Cyberspace: First Steps. Cambridge, Mass. 

Burkert, W. (1990). Antike Mysterien. München. 

Capurro, R. (1996) On the Genealogy of Information. In: K. Kornwachs, K. Jacoby Eds.: Information. New Questions to a Multidisciplinary Concept. Berlin, 259-270.   
- (1996a): Informationsethik nach Kant und Habermas. In: A. Schramm, Hrsg.: Philosophie in Österreich 1996, Wien, 307-310.   
- (1978): Information. München. 

Derrida, J. (1995). Mal d'Archive. Paris. 

Flusser, V. (1996). Kommunikologie. Mannheim. 

Flusser, V. (1994). Vom Subjekt zum Projekt. Menschwerdung. Bensheim. 

Heidegger, M. (1992). Platon: Sophistes. Frankfurt a.M. (GA 19).  

Heim, M. (1994). The Erotic Ontology of Cyberspace. In: Benedikt, M. ed.: Cyberspace: First Steps. Cambridge, Mass. pp. 59-80.   

Negroponte, N. (1995). Being Digital. London. 

Weizsäcker, C.F.v. (1974). Sprache als Information. In: Die Einheit der Natur. München. 

Welsch, W. (1996). Grenzgänge der Ästhetik. Stuttgart.


Last update: February 17, 201$
 
 
 
     

Copyright © 1999 by Rafael Capurro, all rights reserved. This text may be used and shared in accordance with the fair-use provisions of U.S. and international copyright law, and it may be archived and redistributed in electronic form, provided that the author is notified and no fee is charged for access. Archiving, redistribution, or republication of this text on other terms, in any medium, requires the consent of the author. 
 

 
Back to Digital Library
 
Homepage Research Activities
Publications Teaching Video/Audio