Mayer’s spiritual kin are not to be found among the heat-theorists of his time, such as Helmholtz and others, but among thinkers of the stamp of Goethe, Howard and Ruskin. His basic idea of the inner connexion between all forms of energy in nature corresponds entirely with Goethe’s idea of metamorphosis. Just as Goethe saw in the ur-plant the Idea common to all plant-forms or, in the various plant-organs, the metamorphosis of one and the same ur-organ, so was Mayer convinced of the existence of an ur-force which expressed itself in varying guises in the separate energy-forms of nature. In the picture of the physical universe which hovered before him, the transformation of one form of energy into another – such as mechanical energy into electrical, this into chemical and so on – was somewhat similar to Goethe’s picture of the organic life of the earth, in which the metamorphosis of one living form into another constantly occurred. ‘There is in nature’, said Mayer, ‘a specific dimension of immaterial constitution which preserves its value in all changes taking place among the objects observed, whereas its form of appearance alters in the most manifold ways.’