4 As regards the principle underlying the line of consideration followed here, see the remark made in Chapter V in connexion with Goethe's study of the 'proliferated rose' (p. 76f.). CHAPTER XVI Seeing as 'Deed' - II The observation of our own visual process, which we began in the last chapter, will serve now to free us from a series of illusory concepts which have been connected by the onlooker-consciousness with the phenomena brought about by light. There is first the general assumption that light as such is visible. In order to realize that light is itself an invisible agent, we need only consider a few self-evident facts - for instance, that for visibility to arise light must always encounter some material resistance in space. This is, in fact, an encounter between light, typifying levity, and the density of the material world, typifying gravity. Accordingly, wherever visible colours appear we have always to do with light meeting its opposite. Optics, therefore, as a science of the physically perceptible is never concerned with light alone, but always with light and its opposite together. This is actually referred to in Ruskin's statement, quoted in the last chapter, where he speaks of the need of the 'force' and of the intercepting bodily organ before a science of optics can come into existence. Ruskin's 'light', however, is what we have learnt with Goethe to call 'colour', whereas that for which we reserve the term 'light' is called by him simply 'force'. All this shows how illusory it is to speak of 'white' light as synonymous with simple light, in distinction to 'coloured' light. And yet this has been customary with scientists from the time of Newton until today, not excluding Newton's critic, Eddington. In fact, white exists visibly for the eye as part of the manifested world, and is therefore properly characterized as a colour. This is, therefore, how Goethe spoke of it. We shall see presently the special position of white (and likewise of black), as a colour among colours. What matters first of all is to realize that white must be strictly differentiated from light as such, for the function of light is to make visible the material world without itself being visible.