Hegel's philosophical system rested on an appropriation of the concept which lay at the heart of Goethe's scientific work, the Urphänomen (archetypal phenomenon). In a sense, the Urphänomen is the Urphänomen of Hegel's philosophy: Hegel transformed and expanded this idea in his Logic, in which the place of the Urphänomen is taken by a Concept rather than a phenomenon. Marx in turn took this idea as the foundation for Capital, with the practice of commodity exchange being the Urphänomen of bourgeois society; but changed the relationship between conceptual and practical development. Each link in this chain turns the Urphänomen “inside out” in the act of appropriating it.