While leaving a more detailed description of the composition of
Goethe's Entwurf for our next chapter, we shall here deal at once with
some of the essential conclusions to which the reader is led in this
book. As already mentioned, Goethe's first inspection of the
colour-phenomenon produced by the prism had shown him that the
phenomenon depended on the presence of a boundary between light and
darkness. Newton's attempt to explain the spectrum out of light alone
appeared to him, therefore, as an inadmissible setting aside of one of
the two necessary conditions. Colours, so Goethe gleaned directly from
the prismatic phenomenon, are caused by both light and its counterpart,
darkness. Hence, to arrive at an idea of the nature of colour, which
was in accord with its actual appearance, he saw himself committed to
an investigation of the extent to which the qualitative differences in
our experience of colours rests upon their differing proportions of
light and darkness.

It is characteristic of Goethe's whole mode of procedure that he at
once changed the question, 'What is colour?' into the question, 'How
does colour arise?' It was equally characteristic that he did not, as
Newton did, shut himself into a darkened room, so as to get hold of the
colour-phenomenon by means of an artificially set-up apparatus.
Instead, he turned first of all to nature, to let her give him the
answer to the questions she had raised.

It was clear to Goethe that to trace the law of the genesis of colour
in nature by reading her phenomena, he must keep a look-out for
occurrences of colours which satisfied the conditions of the Ur-phänomen,
as he had learned to know it. This meant that he must ask of nature
where she let colours arise out of light and darkness in such a way