There are four ways in which beings supernatural may be conceived as manifesting themselves to human sense. The first, by external types, signs, or influences; as God to Moses in the flames of the bush, and to Elijah in the voice of Horeb.
The second, by the assuming of a form not properly belonging to them; as the Holy Spirit of that of a Dove, the second person of the Trinity of that of a Lamb; and so such manifestations, under Angelic or other form, of the first person of the Trinity, as seem to have been made to Abraham, Moses, and Ezekiel.
The third, by the manifestation of a form properly belonging to them, but not necessarily seen; as of the Risen Christ to his disciples when the doors were shut. And the fourth, by their operation on the human form, which they influence or inspire, as in the shining of the face of Moses.
It is evident that in all these cases, wherever there is form at all, it is the form of some creature to us known. It is no new form peculiar to spirit, nor can it be. We can conceive of none. Our inquiry is simply, therefore, by what modifications those creature forms to us known, as of a lamb, a bird, or a human creature, may be explained as signs or habitations of Divinity, or of angelic essence, and not creatures such as they seem.
This may be done in two ways. First, by effecting some change in the appearance of the creature inconsistent with its actual nature, as by giving it colossal size, or unnatural colour, or material, as of gold, or silver, or flame, instead of flesh, or by taking away its property of matter altogether, and forming it of light or shade, or in an intermediate step, of cloud, or vapour; or explaining it by terrible concomitant circumstances, as of wounds in the body, or strange lights and seemings round about it; or by joining of two bodies together as in angels’ wings. Of all which means of attaining supernatural character (which, though in their nature ordinary and vulgar, are yet effective and very glorious in mighty hands) we have already seen the limits in speaking of the Imagination.
Extract from Ruskin’s Modern Painters, Vol IV, Chapter V ‘Of the Superhuman Ideal’, p. 315