By expressing himself in this way in the Introduction to his Farbenlehre, Goethe makes it clear from the outset that when he speaks of 'light' as the source of colour-phenomena, he has in mind an idea of light very different from that held by modern physics. For in dealing with optics, physical science turns at once to phenomena of light found outside man - in fact to phenomena in that physical realm from which, as the lowest of the kingdoms of nature, the observations of natural science are bound to start. Along this path one is driven, as we have seen, to conceive of light as a mere 'disturbance' in the universe, a kind of irregular chaos. In contrast to this, Goethe sees that to gain an explanation of natural physical phenomena which will be in accord with nature, we must approach them on the path by which nature brings them into being. In the field of light this path is one which leads from light as creative agent to light as mere phenomenon. The highest form of manifestation of creative light most directly resembling its Idea is within man. It is there that light creates for itself the organ through which, as manifest light, it eventually enters into human consciousness. To Goethe it was therefore clear that a theory of light, which is to proceed in accord with nature, should begin with a study of the eye: its properties, its ways of acting when it brings us information of its deeds and sufferings in external nature. The eye with its affinity to light comes into being in the apparently dark space of the mother's womb. This points to the possession by the human organism of an 'inner' light which first forms the eye from within, in order that it may afterwards meet the light outside. It is this inner light that Goethe makes the starting-point of his investigations, and it is for this reason that he treats physiological colours before physical colours. * Of fundamental significance as regards method is the way in which Goethe goes on from the passage quoted above to speak of the activity of the inner light: 'This immediate affinity between light and the eye will be denied by none; to consider them identical in substance is less easy to comprehend. It will be more intelligible to assert that a dormant light resides in the eye, and that this light can be excited by the slightest cause from within or from without. In darkness we can, by an effort of imagination, call up the brightest images; in dreams, objects appear to us as in broad daylight; if we are awake, the slightest external action of light is perceptible, and if the organ suffers a mechanical impact light and colours spring forth.'