In the course of his exposition, Heisenberg also speaks of Goethe, in whose scientific endeavours he perceives a noteworthy attempt to set scientific understanding upon a path other than that of progressive self-restriction.

Just as the conceptual activity has as its bodily foundation the brain, with the nervous appendages, so it is volitional activity which is based on processes taking place in the muscular region of the body and in those organs which provide the body's metabolism.

To understand why this science became restricted to one-eyed, colour-blind observation we need only apply to the human sense system, in particular, what we have learnt concerning man's threefold being.

'The renouncing of life and immediacy, which was the premise for the progress of natural science since Newton, formed the real basis for the bitter struggle which Goethe waged against the physical optics of Newton. It would be superficial to dismiss this struggle as unimportant: there is much significance in one of the most outstanding men directing all his efforts to fighting against the development of Newtonian optics.' There is only one thing for which Heisenberg criticizes Goethe: 'If one should wish to reproach Goethe, it could only be for not going far enough - that is, for having attacked the views of Newton instead of declaring that the whole of Newtonian Physics-Optics, Mechanics and the Law of Gravitation - were from the devil.'

A statement which says that man's will is as directly based on the metabolic processes of the body, both inside and outside the muscles, as is his perceiving and thought-forming mind on a process in the nerves, is bound to cause surprise. Firstly, it seems to leave out the role commonly ascribed to the so-called motoric part of the nervous system in bringing about bodily action; and secondly, the acknowledgment of the dependence of consciousness on corporeal 'dying' implies that willing is an unconscious activity because of its being based on life processes of the body.

Sharply distinguished by their respective modes of functioning though they are, the three bodily systems are each spread out through the whole body and are thus to be found everywhere adjacent to each other. Hence, the corresponding three states of consciousness, the sleeping, dreaming and waking, are also everywhere adjacent and woven into one another. It is the predominance of one or other which imparts a particular quality of soul to one or other region of the body. This is clearly shown within the realm of sense activity, itself the most conscious part of the human being. It is sufficient to compare, say, the senses of sight and smell, and to notice in what different degree we are conscious of the impressions they convey, and how differently the corresponding elements of conception, feeling and willing are blended in each. We never turn away as instinctively from objectionable colour arrangement as from an unpleasant smell. How small a part, on the other hand, do the representations of odours play in our recollection of past experiences, compared with those of sight.⁸ The same is valid in descending measure for all other senses.

Although the full significance of Heisenberg's remarks on Goethe will become apparent only at a later stage of our discussion, they have been quoted here because they form part of the symptom we wish to characterize. Only this much may be pointed out immediately, that Goethe - if not in the scientific then indeed in the poetical part of his writings - did fulfil what Heisenberg rightly feels to have been his true task.²

The first of these two problems will find its answer at a later stage of our discussion when we shall see what entitles us to draw a direct connexion between volition and muscular action. To answer the second problem, simple self-observation is required. This tells us that, when we move a limb, all that we know of is the intention (in its conceptual form) which rouses the will and gives it its direction, and the fact of the completed deed. In between, we accompany the movement with a dim awareness of the momentary positions of the parts of the body involved, so that we know whether or not they are moving in the intended manner. This awareness is due to a particular sense, the 'sense of movement' or 'muscular sense' - one of those senses whose existence physiology has lately come to acknowledge. Nothing, however, is known to us of all the complex changes which are set into play within the muscles themselves in order to carry out some intended movement. And it is these that are the direct outcome of the activity of our will.

Of all senses, the sense of sight has in greatest measure the qualities of a 'conceptual sense'. The experiences which it brings, and these alone, were suitable as a basis for the new science, and even so a further limitation was necessary. For in spite of the special quality of the sense of sight, it is still not free from certain elements of feeling and will - that is, from elements with the character of dream or sleep. The first plays a part in our perception of colour; the second, in observing the forms and perspective ordering of objects we look at.

We mentioned Heisenberg's speech as a symptom of a certain tendency, characteristic of the latest phase in science, to survey critically its own epistemological foundations. A few years previous to Heisenberg's speech, the need of such a survey found an eloquent advocate in the late Professor A. N. Whitehead, in his book Science and the Modern World, where, in view of the contradictory nature of modern physical theories, he insists that 'if science is not to degenerate into a medley of ad hoc hypotheses, it must become philosophical and enter upon a thorough criticism of its own foundations'.