Here we find the eye producing, as usual, a contrast-colour from out of itself, as an after-image, even while its gaze is fixed on the same colour in the outer world. The heightened brilliance within the given field is due to the addition of the after-image colour to the external colour. The reader may wonder why this phenomenon is not immediately adduced as a decisive proof of the fallacy of the whole Newtonian theory of the relation of 'white' light to the various colours. Although it does in fact offer such a proof, we have good reason for not making this use of it here. Throughout this book it is never our intention to enter into a contest of explanations, or to defeat one explanation by another. How little this would help will be obvious if we realize that research was certainly not ignorant of the fact that the opposite colour arises even when the eye is not turned to a white surface. In spite of this, science did not feel its concept of white light as the sum of all the colours to be an error, since it has succeeded in 'explaining' this phenomenon too, and fitting it into the prevailing theory. To do so is in thorough accord with spectator-thinking. Our own concern, however, as in all earlier cases, is to replace this thinking with all its 'proofs' and 'explanations' by learning to read in the phenomena themselves. For no other purpose than this the following facts also are now brought forward. * Besides Rudolf Steiner's fundamental insight into the spiritual-physical nature of the growing human being, through which he laid the basis of a true art of education, he gave advice on many practical points. For example, he indicated how by the choice of a suitable colour environment one can bring a harmonizing influence to bear on extremes of temperament in little children. To-day it is a matter of practical experience that excitable children are quietened if they are surrounded with red or red-yellow colours, or wear clothes of these colours, whereas inactive, lethargic children are roused to inner movement if they are exposed to the influence of blue or blue-green colours.