This nature of sight having never been discovered by the ancient pretenders to natural knowledge; much less by those that consider not things so remote, as that knowledge is, from their present use; it was hard for men to conceive of those images in the fancy and in the sense, otherwise than of things really without us: which some, because they vanish away, they know not whither nor how, will have to be absolutely incorporeal, that is to say, immaterial, or forms without matter; colour and figure, without any coloured or figured body; and that they can put on airy bodies as a garment, to make them visible when they will to our bodily eyes; and others say, are bodies and living creatures, but made of air, or other more subtle and ethereal matter, which is, then, when they will be seen, condensed.