Imagining the future has to take into account the degree to which our reality is conditioned by the existence of substances and materials. The common objects of our present day world, so much taken for granted, would have been unimaginable to people living in an era before their creation, and this is partly because new materials came into existence. Plastics, especially, made so many things possible, from seran wrap to artificial limbs. So if we try to imagine the future, we have to take into account that equally unimaginable objects may come into existence due to the creation of new materials that we do not now possess. Frank Herbert understood this when he imagined buildings constructed of "plasteel".