The Philosophy of the Act
Essay 14 The Perceptual Model in Science
HERE appears to be an important methodological distinction between the perceptual world and the so-called microscopical and submicroscopical world in scientific procedure, though the two shade into each other, as is evidenced in a "model" type of hypothesis and a mathematical type in which the attempt to present the hypothesis in the form of a model is more or less frankly abandoned.
In the perceptual world the physical object is real if it could be conceivably sensed in contact experience, though the contact experience is scientifically stated in mass, with figured dimensions given in vision, which could be conceivably substantiated by contact. In the submicroscopical world such models may be abandoned, and the object be stated in terms of mathematical formulas which present them in relations.
The content of the physical object is stated in terms of energy-mass or electromagnetic. Energy is conceived of as that which is responsible for motion and change in the amount and direction of motion. For its definition it is essential that the physical object should be in a system in which the law of action and reaction holds. Given such a system, it is possible to define a physical object that is a member of the system in terms of the changes within the system for which it is responsible.
In the case of the model, or physical thing in the sense indicated above, the contact is the substance that remain-. unchanged while other characters vary. It is content in the peculiar sense of the rigid body which is used in measurement. That is, it is that which does not change in motion in translation or rotation, and so determines the nature of the space within which the motion takes place. The visual and auditory characters of
(206) the moving object change with motion. It is the effective occupation of tactual space that is the ultimate nature of the physical thing. Newton's definition of mass as the quantity of matter reflects this, as does the use of the rigid body in measurement of Euclidean space and the determination of that space.
The fundamental difference between the two worlds indicated above appears when the changes in mass incident to motion are stated. In terms of quantity of matter the increase in mass with velocity is meaningless or miraculous. The increase in the energy of inertia presents no obvious difficulty.
The difference between the two worlds lies in the difference between the nature of the thing in the two. In the perceptual world the thing is that which fills contact space; in the other world it is energy (that which is responsible for motion within a system of moving bodies). We have abstracted from the perceptual thing and measure this nature in terms of changes. While in the perceptual world we can present this thing in the form of the occupation of space and measure its amount in terms of this quantity, in terms of energy we are dealing with that which has no immediate presentation value but must be realized in its effects. The proportionality of inertial mass and gravitational energy removed the danger of any conflict between the two conceptions of the nature of the physical thing in Newtonian mechanics.
Renaissance physics, in stating the conditions for the sensuous characters of objects in terms of masses in motion, still left the possibility of presenting perceptual models of what takes place in color, sound, odor, and taste. Minute extended things which would have been perceptual to fingers minute enough to feel them involved no contradiction with the thought of them, so that, though the same mechanism was appealed to in explanation of tactual sensations as that which explained the so-called secondary qualities, the imagination was still free to subdivide matter indefinitely and still keep its perceptual models. When we remember that the rigid body that remains what it is when moved in translation or rotation is the presupposition of Euclid-
(207) -ean space, the added importance of these perceptual models can be realized. What is involved here is a spatial figure that has a material filling. If this material filling can be identified with mass, a perceptual model remains possible in scientific hypotheses. If the figure and the energy or what an object is vary with its velocity, a perceptual model becomes inadequate.
It is the electromagnetic investigations which have pushed the submicroscopical field into prominence. Here the nature of the scientific object becomes electricity in some phase. It can not be stated in terms of quantity of matter. While it is subject to spatiotemporal characters, that which undergoes this spatiotemporal definition can in its nature be stated only in terms of energy, i.e., in terms of the motions of a system of objects. It must, therefore, be possible to trace the motions and determine them with exactitude before the content that goes to make up the nature of the scientific object is reached. The question then arises whether we can consider the so-called energy as a characteristic of the system of objects whose changes we measure to determine the energy which is the nature of electrical charge or of the electron or proton. Seemingly, however, the results of scientific analysis compel us to presuppose physical elements which could not have the characters of the objects in the system whose motions we measure in order to determine the energy which is made the nature of the scientific object, e.g., the nucleus of a helium atom whose path we trace in water vapor cannot be stated in terms of the spatial, temporal, and energy u nits which are used within the field within which its changes take place. This is otherwise stated in the transformations of the Maxwell equations which are necessary to render them invariant when they are referred to sets of electromagnetic objects that are moving with reference to the field of observation.
The peculiarity of the submicroscopical field lies not in the minuteness of its elements but in their electromagnetic nature. The results of the work of Maxwell identified light with electromagnetism, while it stated the content of the electromagnetic object in terms of its field of force. The Newtonian conception
(208) of mass as the quantity of matter stated the nature of the object in terms of its spatial dimensions. The physical object was there in advance of its relations to other objects. The system of objects can then be conceived of as built up out of the objects which are logically antecedent. These objects determine also a Euclidean space, as the objective nature of the object does not change with motion. It remains what it is no matter what its velocity or the character of the motion. A body whose nature lies in its field of force cannot be conceived of apart from the system within which the force can operate, i.e., a force implies a motion which it affects, and the measurement of it implies a system within which the quantity of motion can be determined. While one can state the nature of any perceptual body in terms of energy, given its membership in a dynamic system, it has a nature or reality which is independent of this formulation. This reality belongs to it as that which is given in a conceivable contact experience to which a distance character invites. An electromagnetic object, being stated only in terms of fields of force or of energy, has no such conceivably independent character. Force and energy can be stated experientially only in terms of effects. These effects are of something, and the something cannot itself be stated in terms of energy without an indefinite regress. We come back either to the objects of perceptual experience or to a metaphysical thing-in-itself. A scientific imagination may pursue its perceptual object beyond the realm of normal or microscopical vision and thus enter the submicroscopical world and still use perceptual models. The ultimate statement of objects in terms of fields of force or energy allows of no such pursuit. Confusion arises, however, because we locate the object within space and time or within space-time. We determine the position, the mass, the diameter, and the path of the electrical charge, and these all invite the use of perceptual models. The Bohr atom is an outstanding illustration of such a model, in which the content of the object is energy which is spatiotemporally defined. The mathematical physicist, however, escapes from the confinement of these perceptual spatiotemporal forms
(209) by embodying them in mathematical formulas and, by this apparatus, can add any desired dimensions to his space or give it non-Euclidean characters. This situation is further complicated by the doctrine of relativity which teaches that the figured character of the perceptual object changes with the relative velocity of the object, i.e., it reduces the shape and inertia or resistance of the object to secondary characters.
The world to which science refers, then, is submicroscopical in the sense that it implies systems of objects which are presupposed in the definition of energy and have characters which lie beyond our experience. What is revealed in experience is motion that can be spatiotemporally determined.
The spatiotemporal determination of the scientific object under relativistic theory is almost as abstract as the nature of the object. In the first place, the space and time are recognized as conceptual in the sense that they are not the space and time of the perceptual world. There is no right and left or up and down, nor is the time the duration of our immediate experience. Space is conceived in terms of co-ordinates, by means of which position and distances are algebraically stated with reference to an origin and measured on intervals from the co-ordinates. Space thus becomes relative to the origin, or point of reference, and to the unit of measure. As position has to be determined with reference to some co-ordinate whose selection is arbitrary, absolute space disappears; and, as the character of extension depends upon the character of the measuring unit, which may vary its nature in different fields, the structure of space becomes dependent upon the nature of the field of objects. The discovery that a measuring rod from the standpoint of a field of rest, if it is itself in motion with reference to that field of rest, is shorter than it is from the standpoint of the field that is in motion provides another perspective which, since the distortion is dependent upon the velocity of the moving object and its system, may be called a temporal perspective.
The homogeneity of space is indicated in the congruity of the rigid body which is used as a measure in different situations and,
(210) if we conceive of space-time and hence of the passage of space, by the congruity of the rigid body with itself. This still leaves the conception of "straight" undetermined. It is practically determined by the line of vision, i.e., by the line of the ray of light. We sight along the edge of a board and so determine its straightness. Physiologically, we keep the body in line with the distant object toward which we are moving. The distant object is a control by which we continually correct the tendency of the alternate steps of a bilateral system to push the body out of its direction of shortest approach. The shortest distance between two points has, then, a physiological import. It is the line which we keep when we approach a distant object under the control of the visual stimulation of that object. The process is one that also provides a physiological definition of the equality of the steps into which the continuum of the distance as given through vision is divided by walking. Our bilateral symmetry requires that a step from one side should be offset by one from the other, and so arises the functional equality of the series of steps with the continuum of the line of vision. Primarily the line of vision is not itself broken up into equal parts but is achieved by a set of functionally equal units or steps. It is the congruence of the line of vision with the line along which one steps that leads to the division of the continuum into parts. In the field of action the continuum is not divided. When secondarily it is so divided, each portion has the value of the original line of vision which is not itself divided but which is achieved or attained by a set of functionally equal steps. The equality of the continuum to the steps is not immanent in the distance of Achilles from the tortoise but has to be achieved. It follows upon the completed act. The fallacy of the ancient argument lies in identifying the tertiary equality of the distances. of an indefinite set of intermediate goals with the original distance, with the achieved equality of the steps of Achilles to the continuum when he has overtaken the tortoise.
Space, then, appears as the development of the characters of
(211) spatially qualitied. objects within the field of distance stimulation. The object is ultimately that contact experience, for this is the positive or negative goal of the act controlled by the distant stimulation. The act results in contact. Our perception, therefore, tends to correct the distortions of vision at a distance by the characters of contact objects. It is true that we define this object through vision, which is vastly more accurate than contact. The straight edge or line we reach through vision. However, it is a vision that can substantiate immediately its anticipations by the findings of the hand. Within the radius of the arm we have acts which are completed. The distant object as seen is at hand and is handled. It is legitimate to call this perception a collapsed act, and it remains the model of the physical percept; and we tend to supplement either the vision or the feel, where either is absent, but in this field of manipulation distance and contact experience fuse. We even give to the distant object at times the dimensions it would have if close at hand. The space of this field of manipulation is Euclidean. A rigid body is congruent with itself, and the axiom of parallels holds, i.e., the rigid body revolved retains its shape and previous dimensions. The space of Euclidean geometry is the extension of this space of the manipulatory area, in abstraction from all characters except those involved in the system of Cartesian co-ordinates.
The psychological mechanism of seeing the distant object in terms of the field of manipulation can in part be readily conceived. It consists in the assumption of the attitude toward the distant object that we have toward the same object near at hand. We are ready to act toward the distant object as if it were near by. There is, however, a profound difference between seeing the object "in its own dimensions, like itself," and merely acting so as to bring ourselves to the object to manipulate it. The difference may be illustrated in the following of directions by which one reaches a distant goal which one does not place in one's perceptual landscape. Each corner and landmark is a stimulus to turn and proceed in a fashion correspond-
(212) -ing to the directions. When one has reached the goal, one may relate the goal and the path by which one has reached it to one's accustomed landscape. When this is done, the goal has the physical values which all distant objects have for us, those corresponding to attitudes of response which immediate proximity calls out. When we see things in the dimensions and form of the manipulatory area, we are in a measure seeing the distant object in terms of a space which is the extension of the Euclidean space of the manipulatory area, and thus substituting this space for the Riemannian space of vision. Thus we see the elliptical top of the table as round and the corners of the ceilings as right angles. Seeing the ellipse as round and the angle greater than a right angle as a right angle is the control of the visualization by the attitudes of the response belonging to the manipulatory area. It is the control of a Riemannian space by a Euclidean space. We are ready to act toward the shorter diameter of the ellipse as if it were equal to the longer diameter. The extent to which the sensuous content of the percept may be affected by this control is shown in various psychological illusions.
The assumption of the attitudes of response to the physical object within the area of manipulation involves, however, another factor in perception, the response of the thing to our own acts toward it. This is most generally given in what is experienced as the resistance of the physical body, to be clearly distinguished from the pressure of the body as experienced on the surface of our own organisms. What calls for recognition is the reciprocal character of physical objects and the organism. It is the contact of physical objects with the organism and the organism with physical objects that gives to the organism its outside and to physical objects their insides. All physical objects have inside-. in our experience. These insides are never reached by getting inside of them. This process merely exhibits other outsides. The insides arise through the interaction of bodies and the organism. The bodies act upon us, and we act upon the bodies, and this takes place only through interaction. There is
(214) only one source for this acting of the body from its inside and that is the excitement in the organism of the attitude of resistance of the body through the action of the organism upon it. It is through taking the attitude of things about the organism that the organism defines itself over against things. It is this which Whitehead refers to as the "the pushiness of things."
If we trace out these attitudes which are in experience the insides of physical things, we find ourselves presenting them in terms of the operation of elements of the nervous system. The nervous system and its elements, however, belong to the realm of physical things. They may be observed to a certain extent in living organisms, or on the dissecting table, but predominately in imagination of what may be going on within our organisms. It is in this fashion that certain psychologies paradoxically introduce the physical environment into the brain and set up a solipsistic world within the skull. On the contrary, the nervous system in such observations is always outside the observer. Furthermore, the situation within which the organism and its environment are present is a mutual one. If the organism endows the physical things with their insides, the physical things endow the organism with its outside, and thus give it its location and boundaries within the world. An inside has significance only with reference to an outside.
We find in experience as the presupposition of our analysis a world and the organism, or, rather, organisms. This world is real in terms of perception when the act involving the distant field is accomplished and the anticipatory attitudes which this distance field excited have been realized in contact. That is, in the world that is there, in advance of problematic situations and reflection, uncertainty and hypothesis are present in the distance field. Uncertainty shows itself in alternative possible responses answering to different possible objects, and hypothesis is represented in the tentative character of the object-the organism is ready to discover differences in the object as approach and contact ensue. Immediate experience also carries with it
(214) the dependence of the character of the distant object upon the relative position and sensitivity of the organism. The active processes of sensing-spying, sniffing, listening-as well as the selective character of perception, carry with them the involvement of the organism in the form which the percept assumes. Relativity and the triadic relation of the distant object, its nature, and the organism are but reflective developments of characters of immediate experience. In immediate experience the object is what it is in the manipulatory area, when hand and eye agree. Up to this point there is uncertainty, and tentative organization of the object.