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Author’s Note

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Compared with the more refined methods of present-day thought, Hooke’s procedure may strike us as somewhat primitive. Actually he did nothing more than has since been done times without number; for the scientist has become more and more willing to allow artificially evoked sense-perceptions to dictate the thoughts he uses in forming a scientific picture of the world.

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For his investigation Hooke chose the point of a needle and a knife-edge, as providing the best representatives among physical objects of point and straight line. In the sketches here reproduced we may see how Hooke made clear to his readers how little these two things, when observed through the microscope, resemble what is seen by the unaided eye. This fact convinced Hooke that the apparent agreement between the world of perception and the world of ideas rests on nothing more solid than an optical limitation (Plate I).

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Of all the ideas that human reason can form, Hooke considered the simplest and the most fundamental to be the geometrical concepts of point and straight line. Undoubtedly we are able to think these, but the naïve consciousness takes for granted that it also perceives them as objective realities outside itself, so that thoughts and facts correspond to each other. We must now ask, however, if this belief is not due to an optical deception. Let us turn to the microscope and see what point and line in the external world look like through 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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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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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 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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Of these utterances, Eddington’s is at the present point of our discussion of special interest for us; for he outlines in it the precise field of sense-perception into which science has withdrawn in the course of that general retreat towards an ever more restricted questioning of nature which was noted by Heisenberg.

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Let us listen to yet another voice from the ranks of present-day science, expressing a criticism which is symptomatic of our time. It comes from the late physiologist, Professor A, Carrel, who, concerning the effect which scientific research has had on man’s life in general, says in his book, Man the Unknown: ‘The sciences of inert matter have led us into a country that is not ours. … Man is a stranger in the world he has created.’