Mental “structures” in the Berlin school of Gestalt Psychology: can sensation be described as “structural”? Eric TREMAULT Phico/Execo, Université Paris 1 Panthéon-Sorbonne Abstract. It is not exaggerated to affirm that the modern notion of structure arises in Koffka’s Growth of the Mind and in his following article, “Perception : An introduction to the Gestalt-theorie” (1922). The importance of the notion of structure as Koffka uses it lies in the fact that it is designed to replace the old empiricist notion of “sensation” as a real and separable element of the phenomenal field, corresponding to a definite stimulus. But, yielding to many suggestions by Köhler, Koffka does not only understand the interdependency of sensations in a structure as a causal one: in fact, he decidedly understands it as a logical one. Thus he defines structures as “very elementary reactions, which phenomenally are not composed of constituent elements, their members being what they are by virtue of their ‘member-character,’ their place in the whole; their essential nature being derived from the whole whose members they are” (“Perception”, p.543). I mean to show that the parts in such structures can only be what it is classical to name “relational attributes” or “relational predicates”. In other words, structures are now internal relations between their terms, and more precisely still “directly constitutive internal relations”, not internal relations reducing to the existence of their terms as were the internal relations against which Russell struggled, but relations to which their terms reduce. But the real importance of this notion of structure is that it rests and is built upon a truly impressive amount of empirical data. Nevertheless, I want to show that Koffka’s conception of sensation is fundamentally impossible to conceive, and that the belief that it is empirically grounded rests mainly on a confusion between abstraction of a sense-datum and real separation of the stimuli underlying such a datum. As a consequence, phenomenal structures, if they exist, can only be external to their terms, as they are in Köhler’s view, in spite of many ambiguities in his formulations. However, I will end by showing that, correctly understood, the notion of structure can still be of great help in phenomenology and psychology since it provides a naturalistic means to understand how a non-intentional “meaning” can be passively present at a sensory level. Keywords: Structure ; Internal relations ; Sensation ; Gestalt psychology ; Phenomenology Introduction My main aim in this paper is to object to any kind of “structural” theory concerning sensation, meaning by this any theory which claims that one cannot attribute a relation to a sensorial content without intrinsically altering it. In philosophical terms, such a theory would refuse to acknowledge a distinction between “knowledge by acquaintance” and “knowledge about”: it would argue that all so-called “knowledge by 151 acquaintance” is only knowledge so far as it is knowledge of the relations of a sensorial content, and that this content itself is ultimately reducible to those relations. Thus, a “structural theory of sensation” is essentially emphasizing the primacy of relations over sensations. Such was the neo-Hegelian approach to sensation at the end of the Nineteenth Century, whose most famous representatives were T.H. Green and F.H. Bradley. As William James put it in his Principles of Psychology ([1],[2]), quoting T.H. Green: “The only reals for the neo-Hegelian writers appear to be relations, relations without terms, or whose terms are speciously such and really consist in knots, or gnarls relations finer still in infinitum. ‘Exclude from what we have considered real all qualities constituted by relation, we find that none are left’ ‘Abstract the many relations from the one thing and there is nothing … Without relations it would not exist at all.’ [T. H. Green, Prolegomena to Ethics, §§ 20, 28.] ‘The single feeling is nothing real.’ ‘On the recognition of relations as constituting the nature of ideas, rests the possibility of any tenable theory of their reality.’ [Introduction to Hume, §§ 146, 188.]” ([2], p. 10). Thus, it is T.H. Green who first developed most clearly a “structural theory” concerning sensation. Bradley’s point of view is more complex (as was particularly well shown by Peter Hylton [3]), since he also tried to reduce all external relations to internal relations, but then wanted to prove the unreality of internal relations themselves: for what he really tried to demonstrate was the unreality of all kinds of relations. Following the path of Russell and William James most notoriously, I shall then reject Bradley’s first move, and defend externals relations against their reduction to internal ones; but then I shall nonetheless take over the arguments Bradley uses in his second move, against certain kinds of internal relations. However, it is less known, and more directly interesting to us here, that the Berlin school of Gestalt psychology, when it first introduced the notion of “structure” in its contemporary meaning in psychology and philosophy, was itself mainly concerned with developing such a structural theory of sensation, in the neo-Hegelian sense just used. But it seems nevertheless that Gestalt psychologists never had any kind of a priori bias or leaning towards neo-Hegelian thinking when developing this notion of “structure” as it is still used today, and on the contrary always showed public disdain for what they called “romantic” theories of nature1. Even this disdain itself was only formulated as an answer to psychologists who precisely read Gestalt psychology as a new kind of neo-Hegelianism. Hence, there is no reason to think that this disdain was simulated, and more reason to think that Gestalt psychologists only discovered the possibility of tracing their theories back to neo-Hegelianism when reading the commentaries of others. Indeed, it is mainly Kurt Koffka who, among Berlin Gestalt psychologists, clearly developed a structural theory of sensations in Die Grundlagen der psychischen Entwicklung (1921, translated as [7] in 1924, first edition), and in his following article in English, “Perception : An introduction to the Gestalt-theorie” (1922, [8]), but this structural theory almost entirely disappeared in his late master work, Principles of Gestalt Psychology (1935, [9]), which largely explains why this aspect of Gestalt psychology seems to be widely ignored today, even though it remains as one of the central reasons for the influence of this school, especially among philosophers such 1 See Köhler [4], pp. 153 f. ([5], p. 30), and especially his detailed answer to G.E. Müller on this question in [6] ([5], pp. 379 f.). 152 as Merleau-Ponty, Cassirer and Scheler. Now, as far as I know, Koffka never clearly explained why he had to abandon his initial theory, but the fact that it finally appeared to him linked with neo-Hegelianism may very well be one of the reasons for this disappearance. Nevertheless, I want to show that there are other reasons which go much deeper than this one. But what I wanted first to emphasize is that, not being interested at all in neo-Hegelian thought, the only reason why Gestalttheory ended up formulating a new kind of structural theory of sensation is that such a theory seems at first glance to rest on facts. This is what makes it so difficult to untangle the intellectual situation surrounding such structural theories even today: for a great number of psychological facts seem to support them, even though, as I intend to show, those theories will prove to be logically impossible to conceive. In this paper, I want to focus on this theoretical and logical impossibility of the notion of “structure” as Koffka first introduced it, and as it is still used today when precisely employed. But, as it seems to me that the real importance of this notion is that it rests and is built upon a truly impressive amount of empirical data, I need to begin with a paradigmatic example that will reveal its prima facie legitimacy. 1. Empirical data in favor of a “structural theory of sensation” For this purpose, I will quickly present the phenomenon known since Jaensch as the phenomenon of “colour-transformation”, a phenomenon that Koffka lays great stress on since he uses it to interpret the chromatic constancy phenomena as well2. Koffka thus shows that all colours appear and are qualitatively determined upon a general “chromatic level” which may correspond to any objective colour stimulus but always appears as a neutral white, while the phenomenal colour of the other stimuli (which generally appear as “figures” upon this “ground”) depends upon their difference or “gradient” from the “level” stimuli. As a matter of fact, these level stimuli generally correspond approximately to the center of the chromatic scale of the present stimuli, and it is the relation of the surrounding stimuli to this chromatic center that determines the phenomenal colour those stimuli will appear with. Most of the time, the chromatic center is the chromatic value of the general lighting, so that the colour of this lighting will tend to phenomenally disappear, while the phenomenal colour of all stimuli will depend on their objective difference from the lighting stimuli. This explains why the figures we actually see always tend to appear with the same colour they “truly” have, even when seen under coloured lightings: inasmuch as the lighting covers both figure and ground, the “gradient” between them remains constant, whatever the objective colour of the lighting may be. But the “colour-transformation” phenomenon is most striking when the light on the figure is isolated, while the lighting on the ground is slowly changed. For, this time, the objective difference between the stimuli corresponding to figure and ground is accordingly modified, and the result is that the ground remains phenomenally constant while the colour of the figure changes under our eyes.