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The conception of Indeterminacy as an unavoidable consequence of the latest phase of physical research is due to Professor W. Heisenberg. Originally this conception forced itself upon Heisenberg as a result of experimental research. In the meantime the same idea has received its purely philosophical foundation. We shall here deal with both lines of approach.
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After the discovery by Galileo of the parallelogram of forces, it became the object of classical physics – unexpressed, indeed, until Newton wrote his Principia – to bring the unchanging laws ruling nature into the light of human consciousness, and to give them conceptual expression in the language of mathematical formulae. Since, however, science was obliged to restrict itself to what could be observed with a single, colour-blind eye, physics has taken as its main object of research the spatio-temporal relationships, and their changes, between discrete, ideally conceived, point-like particles. Accordingly, the mathematically formulable laws holding sway in nature came to mean the laws according to which the smallest particles in the material foundation of the world change their position with regard to each other. A science of this kind could logically maintain that, if ever it succeeded in defining both the position and the state of motion, in one single moment, of the totality of particles composing the universe, it would have discovered the law on which universal existence depends. This necessarily rested on the presupposition that it really was the ultimate particles of the physical world which were under observation. In the search for these, guided chiefly by the study of electricity, the physicists tracked down ever smaller and smaller units; and along this path scientific research has arrived at the following peculiar situation.
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In his isolation as world spectator, the modern philosopher was bound to reach two completely opposite views regarding the objective value of human thought. One of these was given expression in Descartes’ famous words: Cogito ergo sum (‘I think, therefore I am’). Descartes (1596-1650), rightly described as the inaugurator of modern philosophy, thus held the view that only in his own thought-activity does man find a guarantee of his own existence.
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To observe any object in the sense world we need an appropriate medium of observation. For ordinary things, light provides this. In the sense in which light is understood to-day, this is possible because the spatial extension of the single light impulses, their so-called wavelength, is immeasurably smaller than the average magnitude of all microscopically visible objects. This ensures that they can be observed clearly by the human eye. Much smaller objects, however, will require a correspondingly shorter wave-length in the medium of observation. Now shorter wave-lengths than those of visible light have been found in ultra-violet light and in X-rays; and these, accordingly, are now often used for minute physical research.
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In coming to this view, Descartes took as his starting-point his experience that human consciousness contains only the thought pictures evoked by sense-perception, and yet knows nothing of the how and why of the things responsible for such impressions. He thus found himself compelled, in the first place, to doubt whether any of these things had any objective existence, at all. Hence, there remained over for him only one indubitable item in the entire content of the universe – his own thinking; for were he to doubt even this, he could do so only by again making use of it. From the ‘I doubt, therefore I am’, he was led in this way to the ‘I think, therefore I am’.
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In this way, however, we are led by nature to a definite boundary; for we now find ourselves in a realm where the dimensions of the observation medium and the observed object are more or less the same. The result, unfortunately, is that when the ‘light’ meets the object, it changes the latter’s condition of movement. On the other hand, if a ‘light’ is used whose wave-length is too big to have any influence on the object’s condition of movement, it precludes any exact determination of the object’s location.
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The other conception of human thought reached by the onlooker-consciousness was diametrically opposed to that of Descartes, and entirely cancelled its conceptual significance. It was put forward – not long afterwards – by Robert Hooke (1635-1703), the first scientist to make systematic use of the newly invented microscope by means of which he made the fundamental discovery of the cellular structure of plant tissues. It was, indeed, on the strength of his microscopic studies that he boldly undertook to determine the relationship of human thought to objective reality. He published his views in the introduction to his Micrographia, the great work in which, with the lavish help of carefully executed copper engravings, he made his microscopic observations known to the world.
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Thus, having arrived at the very ground of the world – that is, where the cosmic laws might be expected to reveal themselves directly – the scientist finds himself in the remarkable situation of only being able to determine accurately either the position of an observed object and not its state of motion, or its state of motion and not its position. The law he seeks, however, requires that both should be known at the same time. Nor is this situation due to the imperfection of the scientific apparatus employed, but to its very perfection, so that it appears to arise from the nature of the foundation of the world – in so far, at least, as modern science is bound to conceive it.
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Hooke’s line of thought is briefly as follows: In past ages men subscribed to the naive belief that what they have in their consciousness as thought pictures of the world, actually reproduces the real content of that world. The microscope now demonstrates, however, how much the familiar appearance of the world depends on the structure of our sense apparatus; for it reveals a realm just as real as that already known to us, but hitherto concealed from us because it is not accessible to the natural senses. Accordingly, if the microscope can penetrate through the veil of illusion which normally hides a whole world of potentially visible phenomena, it may be that it can even teach us something about the ideas we have hitherto formed concerning the nature of things. Perhaps it can bring us a step nearer the truth in the sphere of thought, as it so obviously has done in that of observation.
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If it is true that a valid scientific knowledge of nature is possible only in the sphere open to a single-eyed, colour-blind observation, and if it is true – as a science of this kind, at any rate, is obliged to believe – that all processes within the material foundation of the world depend on nothing but the movements of certain elementary particles of extremely small size, then the fact must be faced that the very nature of these processes rules out the discovery of any stable ordering of things in the sense of mathematically formulable laws. The discovery of such laws will then always be the last step but one in scientific investigation; the last will inevitably be the dissolution of such laws into chaos. For a consistent scientific thinking that goes this way, therefore, nothing is left but to recognize chaos as the only real basis of an apparently ordered world, a chaos on whose surface the laws that seem to hold sway are only the illusory picturings of the human mind. This, then, is the principle of Indeterminacy as it has been encountered in the course of practical investigation into the electrical processes within physical matter.