These considerations from the sphere of Physics are supplemented by the Psycho-physicists with their doctrine of specific sense-energies. J. Müller has shown that every sense can be affected only in its own characteristic way as determined by its organisation, and that its reaction is always of the same kind whatever may be the external stimulus. If the optical nerve is stimulated, light-sensations are experienced by us regardless of whether the stimulus was pressure, or an electric current, or light. On the other hand, the same external phenomena produce quite different sensations according as they are perceived by different senses. From these facts the inference has been drawn that there occurs only one sort of phenomenon in the external world, viz., motions, and that the variety of qualities of the world we perceive is essentially a reaction of our senses to these motions. According to this view, we do not perceive the external world as such, but only the subjective sensations which it evokes in us.
Physiology adds its quota to the physical arguments. Physics deals with the phenomena which occur outside our organisms and which correspond to our percepts. Physiology seeks to investigate the processes which go on in man’s own body when a certain sensation is evoked in him. It teaches us that the epidermis is wholly insensitive to the stimuli in the external world. Thus, e.g., if external stimuli are to affect the end-organs of our touch-nerves on the surface of our bodies, the oscillations which occur outside our bodies have to be transmitted through the epidermis. In the case of the senses of hearing and of sight, the external motions have, in addition, to be modified by a number of structures in the sense-organs, before they reach the nerves. The nerves have to conduct the effects produced in the end-organs up to the central organ, and only then can take place the process by means of which purely mechanical changes in the brain produce sensations. It is clear that the stimulus which acts upon the sense-organs is so completely changed by the transformations which it undergoes, that every trace of resemblance between the initial impression on the sense-organs and the final sensation in consciousness must be obliterated. Hartmann sums up the outcome of these considerations in these words: “This content of consciousness consists, originally, of sensations which are the reflex responses of the soul to the molecular motions in the highest cortical centres, but which have not the faintest resemblance to the molecular motions by which they are elicited.”
If we think this line of argument through to the end, we must agree that, assuming it to be correct, there survives in the content of our consciousness not the least element of what may be called “external existence.”
To the physical and physiological objections against so-called “Naïve Realism” Hartmann adds some further objections which he describes as philosophical in the strict sense. A logical examination of the physical and physiological objections reveals that, after all, the desired conclusion can be reached only if we start from the existence and nexus of external objects, just as these are assumed by the ordinary naïve consciousness, and then inquire how this external world can enter the consciousness of beings with organisms such as ours. We have seen that every trace of such an external world is lost on the way from the impression on the sense-organ to the appearance of the sensation in our consciousness, and that in the latter nothing survives except our ideas. Hence, we have to assume that the picture of the external world which we actually have, has been built up by the soul on the basis of the sensations given to it. First, the soul constructs out of the data of the senses of touch and sight a picture of the world in space, and then the sensations of the other senses are fitted into this space-system. When we are compelled to think of a certain complex of sensations as belonging together, we are led to the concept of substance and regard substance as the bearer of sense-qualities. When we observe that some sense-qualities disappear from a substance and that others appear in their place, we ascribe this event in the world of phenomena to a change regulated by the law of causality. Thus, according to this view, our whole world-picture is composed of subjective sensations which are ordered by the activity of our own souls. Hartmann says, “What the subject perceives is always only modifications of its own psychic states and nothing else.”[9]
Now let us ask ourselves, How do we come by such a view? The bare skeleton of the line of thought which leads to it is as follows. Supposing an external world exists, we do not perceive it as such but transform it through our organisation into a world of ideas. This is a supposition which, when consistently thought out, destroys itself. But is this reflection capable of supporting any positive alternative? Are we justified in regarding the world, which is given to us, as the subjective content of ideas because the assumptions of the naïve consciousness, logically followed out, lead to this conclusion? Our purpose is, rather, to exhibit these assumptions themselves as untenable. Yet, so far we should have found only that it is possible for a premise to be false and yet for the conclusion drawn from it to be true. Granted that this may happen, yet we can never regard the conclusion as proved by means of that premise.
It is usual to apply the title of “Naïve Realism” to the theory which accepts as self-evident and indubitable the reality of the world-picture which is immediately given to us. The opposite theory, which regards this world as merely the content of our consciousness, is called “Transcendental Idealism.” Hence, we may sum up the outcome of the above discussion by saying, “Transcendental Idealism demonstrates its own truth, by employing the premises of the Naïve Realism which it seeks to refute.” Transcendental Idealism is true, if Naïve Realism is false. But the falsity of the latter is shown only by assuming it to be true. Once we clearly realise this situation, we have no choice but to abandon this line of argument and to try another. But are we to trust to good luck, and experiment about until we hit by accident upon the right line? This is Eduard von Hartmann’s view when he believes himself to have shown the validity of his own epistemological standpoint, on the ground that his theory explains the phenomena whereas its rivals do not. According to his view, the several philosophical systems are engaged in a sort of struggle for existence in which the fittest is ultimately accepted as victor. But this method appears to us to be unsuitable, if only for the reason that there may well be several hypotheses which explain the phenomena equally satisfactorily. Hence, we had better keep to the above line of thought for the refutation of Naïve Realism, and see where precisely its deficiency lies. For, after all, Naïve Realism is the view from which we all start out. For this reason alone it is advisable to begin by setting it right. When we have once understood why it must be defective, we shall be led upon the right path with far greater certainty than if we proceed simply at haphazard.
The subjectivism which we have sketched above is the result of the elaboration of certain facts by thought. Thus, it takes for granted that, from given facts as starting-point, we can by consistent thinking, i.e., by logical combination of certain observations, gain correct conclusions. But our right thus to employ our thinking remains unexamined. There, precisely, lies the weakness of this method. Whereas Naïve Realism starts from the unexamined assumption that the contents of our perceptual experience have objective reality, the Idealism just described starts from the no less unexamined conviction that by the use of thought we can reach conclusions which are scientifically valid. In contrast to Naïve Realism, we may call this point of view “Naïve Rationalism.” In order to justify this term, it may be well to insert here a brief comment on the concept of the “Naïve.” A. Döring, in his essay Über den Begriff des Naiven Realismus,[10] attempts a more precise determination of this concept. He says, “The concept of the Naïve marks as it were the zero-point on the scale of our reflection upon our own activity. In content the Naïve may well coincide with the True, for, although the Naïve is unreflecting and, therefore, uncritical or a-critical, yet this lack of reflection and criticism excludes only the objective assurance of truth. It implies the possibility and the danger of error, but it does not imply the necessity of error. There are naïve modes of feeling and willing as there are naïve modes of apprehending and thinking, in the widest sense of the latter term. Further, there are naïve modes of expressing these inward states in contrast with their repression or modification through consideration for others and through reflection. Naïve activity is not influenced, at least not consciously, by tradition, education, or imposed rule. It is in all spheres (as its root nativus, brings out), unconscious, impulsive, instinctive, dæmonic activity.” Starting from this account, we will try to determine the concept of the Naïve still more precisely. In every activity we may consider two aspects—the activity itself and our consciousness of its conformity to a law. We may be wholly absorbed in the former, without caring at all for the latter. The artist is in this position, who does not know in reflective form the laws of his creative activity but yet practises these laws by feeling and sense. We call him “naïve.” But there is a kind of self-observation which inquires into the laws of one’s own activity and which replaces the naïve attitude, just described, by the consciousness of knowing exactly the scope and justification of all one does. This we will call “critical.” This account seems to us best to hit off the meaning of this concept which, more or less clearly understood, has since Kant acquired citizen-rights in the world of philosophy. Critical reflection is, thus, the opposite of naïve consciousness. We call an attitude “critical” which makes itself master of the laws of its own activity in order to know how far it can rely on them and what are their limits. Theory of Knowledge can be nothing if not a critical science. Its object is precisely the most subjective activity of man—knowing. What it aims at exhibiting is the laws to which knowing conforms. Hence, the naïve attitude is wholly excluded from this science. Its claim to strength lies precisely in that it achieves what many minds, interested in practice rather than in theory, pride themselves on never having attempted, viz., “thinking about thought.”
[2] Zur Analyse der Wirklichkeit (Strassburg, 1876), p. 28. [↑]